From 7d87da8acdd3b8817d941b9a172be6282722bf5e Mon Sep 17 00:00:00 2001
From: Anthony Sottile <asottile@umich.edu>
Date: Thu, 11 Jan 2018 21:41:48 -0800
Subject: [PATCH] Move PrefixedCommandRunner -> Prefix

---
 pre_commit/languages/all.py           |  14 ++-
 pre_commit/languages/docker.py        |  28 +++---
 pre_commit/languages/docker_image.py  |   2 +-
 pre_commit/languages/golang.py        |  22 ++---
 pre_commit/languages/helpers.py       |   8 +-
 pre_commit/languages/node.py          |  27 +++---
 pre_commit/languages/pcre.py          |   2 +-
 pre_commit/languages/pygrep.py        |   2 +-
 pre_commit/languages/python.py        |  29 +++---
 pre_commit/languages/ruby.py          |  51 +++++-----
 pre_commit/languages/script.py        |   4 +-
 pre_commit/languages/swift.py         |  19 ++--
 pre_commit/languages/system.py        |   2 +-
 pre_commit/prefix.py                  |  20 ++++
 pre_commit/prefixed_command_runner.py |  50 ----------
 pre_commit/repository.py              |  62 ++++++------
 tests/conftest.py                     |   6 --
 tests/languages/all_test.py           |   6 +-
 tests/languages/ruby_test.py          |  39 ++++----
 tests/prefix_test.py                  |  57 +++++++++++
 tests/prefixed_command_runner_test.py | 133 --------------------------
 tests/repository_test.py              |  30 +++---
 tests/util_test.py                    |  29 ++++++
 23 files changed, 270 insertions(+), 372 deletions(-)
 create mode 100644 pre_commit/prefix.py
 delete mode 100644 pre_commit/prefixed_command_runner.py
 create mode 100644 tests/prefix_test.py
 delete mode 100644 tests/prefixed_command_runner_test.py

diff --git a/pre_commit/languages/all.py b/pre_commit/languages/all.py
index 514ba611..a56f7e79 100644
--- a/pre_commit/languages/all.py
+++ b/pre_commit/languages/all.py
@@ -23,25 +23,25 @@ from pre_commit.languages import system
 #     return 'default' if there is no better option.
 #    """
 #
-# def healthy(repo_cmd_runner, language_version):
+# def healthy(prefix, language_version):
 #     """Return whether or not the environment is considered functional."""
 #
-# def install_environment(repo_cmd_runner, version, additional_dependencies):
+# def install_environment(prefix, version, additional_dependencies):
 #     """Installs a repository in the given repository.  Note that the current
 #     working directory will already be inside the repository.
 #
 #     Args:
-#         repo_cmd_runner - `PrefixedCommandRunner` bound to the repository.
+#         prefix - `Prefix` bound to the repository.
 #         version - A version specified in the hook configuration or
 #             'default'.
 #     """
 #
-# def run_hook(repo_cmd_runner, hook, file_args):
+# def run_hook(prefix, hook, file_args):
 #     """Runs a hook and returns the returncode and output of running that
 #     hook.
 #
 #     Args:
-#         repo_cmd_runner - `PrefixedCommandRunner` bound to the repository.
+#         prefix - `Prefix` bound to the repository.
 #         hook - Hook dictionary
 #         file_args - The files to be run
 #
@@ -62,6 +62,4 @@ languages = {
     'swift': swift,
     'system': system,
 }
-
-
-all_languages = languages.keys()
+all_languages = sorted(languages)
diff --git a/pre_commit/languages/docker.py b/pre_commit/languages/docker.py
index f5eed752..f3c46a33 100644
--- a/pre_commit/languages/docker.py
+++ b/pre_commit/languages/docker.py
@@ -22,10 +22,9 @@ def md5(s):  # pragma: windows no cover
     return hashlib.md5(five.to_bytes(s)).hexdigest()
 
 
-def docker_tag(repo_cmd_runner):  # pragma: windows no cover
-    return 'pre-commit-{}'.format(
-        md5(os.path.basename(repo_cmd_runner.path())),
-    ).lower()
+def docker_tag(prefix):  # pragma: windows no cover
+    md5sum = md5(os.path.basename(prefix.prefix_dir)).lower()
+    return 'pre-commit-{}'.format(md5sum)
 
 
 def docker_is_running():  # pragma: windows no cover
@@ -41,39 +40,36 @@ def assert_docker_available():  # pragma: windows no cover
     )
 
 
-def build_docker_image(repo_cmd_runner, **kwargs):  # pragma: windows no cover
+def build_docker_image(prefix, **kwargs):  # pragma: windows no cover
     pull = kwargs.pop('pull')
     assert not kwargs, kwargs
     cmd = (
         'docker', 'build',
-        '--tag', docker_tag(repo_cmd_runner),
+        '--tag', docker_tag(prefix),
         '--label', PRE_COMMIT_LABEL,
     )
     if pull:
         cmd += ('--pull',)
     # This must come last for old versions of docker.  See #477
     cmd += ('.',)
-    helpers.run_setup_cmd(repo_cmd_runner, cmd)
+    helpers.run_setup_cmd(prefix, cmd)
 
 
 def install_environment(
-        repo_cmd_runner, version, additional_dependencies,
+        prefix, version, additional_dependencies,
 ):  # pragma: windows no cover
-    assert repo_cmd_runner.exists('Dockerfile'), (
-        'No Dockerfile was found in the hook repository'
-    )
     helpers.assert_version_default('docker', version)
     helpers.assert_no_additional_deps('docker', additional_dependencies)
     assert_docker_available()
 
-    directory = repo_cmd_runner.path(
+    directory = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
     )
 
     # Docker doesn't really have relevant disk environment, but pre-commit
     # still needs to cleanup it's state files on failure
     with clean_path_on_failure(directory):
-        build_docker_image(repo_cmd_runner, pull=True)
+        build_docker_image(prefix, pull=True)
         os.mkdir(directory)
 
 
@@ -90,15 +86,15 @@ def docker_cmd():
     )
 
 
-def run_hook(repo_cmd_runner, hook, file_args):  # pragma: windows no cover
+def run_hook(prefix, hook, file_args):  # pragma: windows no cover
     assert_docker_available()
     # Rebuild the docker image in case it has gone missing, as many people do
     # automated cleanup of docker images.
-    build_docker_image(repo_cmd_runner, pull=False)
+    build_docker_image(prefix, pull=False)
 
     hook_cmd = helpers.to_cmd(hook)
     entry_exe, cmd_rest = hook_cmd[0], hook_cmd[1:]
 
-    entry_tag = ('--entrypoint', entry_exe, docker_tag(repo_cmd_runner))
+    entry_tag = ('--entrypoint', entry_exe, docker_tag(prefix))
     cmd = docker_cmd() + entry_tag + cmd_rest
     return xargs(cmd, file_args)
diff --git a/pre_commit/languages/docker_image.py b/pre_commit/languages/docker_image.py
index a6f89e3f..6301970c 100644
--- a/pre_commit/languages/docker_image.py
+++ b/pre_commit/languages/docker_image.py
@@ -13,7 +13,7 @@ healthy = helpers.basic_healthy
 install_environment = helpers.no_install
 
 
-def run_hook(repo_cmd_runner, hook, file_args):  # pragma: windows no cover
+def run_hook(prefix, hook, file_args):  # pragma: windows no cover
     assert_docker_available()
     cmd = docker_cmd() + helpers.to_cmd(hook)
     return xargs(cmd, file_args)
diff --git a/pre_commit/languages/golang.py b/pre_commit/languages/golang.py
index cad7dfc6..35cfa2ad 100644
--- a/pre_commit/languages/golang.py
+++ b/pre_commit/languages/golang.py
@@ -26,8 +26,8 @@ def get_env_patch(venv):
 
 
 @contextlib.contextmanager
-def in_env(repo_cmd_runner):
-    envdir = repo_cmd_runner.path(
+def in_env(prefix):
+    envdir = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
     )
     with envcontext(get_env_patch(envdir)):
@@ -50,20 +50,18 @@ def guess_go_dir(remote_url):
         return 'unknown_src_dir'
 
 
-def install_environment(repo_cmd_runner, version, additional_dependencies):
+def install_environment(prefix, version, additional_dependencies):
     helpers.assert_version_default('golang', version)
-    directory = repo_cmd_runner.path(
+    directory = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
     )
 
     with clean_path_on_failure(directory):
-        remote = git.get_remote_url(repo_cmd_runner.path())
+        remote = git.get_remote_url(prefix.prefix_dir)
         repo_src_dir = os.path.join(directory, 'src', guess_go_dir(remote))
 
         # Clone into the goenv we'll create
-        helpers.run_setup_cmd(
-            repo_cmd_runner, ('git', 'clone', '.', repo_src_dir),
-        )
+        helpers.run_setup_cmd(prefix, ('git', 'clone', '.', repo_src_dir))
 
         if sys.platform == 'cygwin':  # pragma: no cover
             _, gopath, _ = cmd_output('cygpath', '-w', directory)
@@ -75,10 +73,10 @@ def install_environment(repo_cmd_runner, version, additional_dependencies):
         for dependency in additional_dependencies:
             cmd_output('go', 'get', dependency, cwd=repo_src_dir, env=env)
         # Same some disk space, we don't need these after installation
-        rmtree(repo_cmd_runner.path(directory, 'src'))
-        rmtree(repo_cmd_runner.path(directory, 'pkg'))
+        rmtree(prefix.path(directory, 'src'))
+        rmtree(prefix.path(directory, 'pkg'))
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
-    with in_env(repo_cmd_runner):
+def run_hook(prefix, hook, file_args):
+    with in_env(prefix):
         return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/languages/helpers.py b/pre_commit/languages/helpers.py
index 30082d6b..ddbe2e80 100644
--- a/pre_commit/languages/helpers.py
+++ b/pre_commit/languages/helpers.py
@@ -5,8 +5,8 @@ import shlex
 from pre_commit.util import cmd_output
 
 
-def run_setup_cmd(runner, cmd):
-    cmd_output(*cmd, cwd=runner.prefix_dir, encoding=None)
+def run_setup_cmd(prefix, cmd):
+    cmd_output(*cmd, cwd=prefix.prefix_dir, encoding=None)
 
 
 def environment_dir(ENVIRONMENT_DIR, language_version):
@@ -39,9 +39,9 @@ def basic_get_default_version():
     return 'default'
 
 
-def basic_healthy(repo_cmd_runner, language_version):
+def basic_healthy(prefix, language_version):
     return True
 
 
-def no_install(repo_cmd_runner, version, additional_dependencies):
+def no_install(prefix, version, additional_dependencies):
     raise AssertionError('This type is not installable')
diff --git a/pre_commit/languages/node.py b/pre_commit/languages/node.py
index aca3c410..5f5d9fdd 100644
--- a/pre_commit/languages/node.py
+++ b/pre_commit/languages/node.py
@@ -33,8 +33,8 @@ def get_env_patch(venv):  # pragma: windows no cover
 
 
 @contextlib.contextmanager
-def in_env(repo_cmd_runner, language_version):  # pragma: windows no cover
-    envdir = repo_cmd_runner.path(
+def in_env(prefix, language_version):  # pragma: windows no cover
+    envdir = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, language_version),
     )
     with envcontext(get_env_patch(envdir)):
@@ -42,31 +42,26 @@ def in_env(repo_cmd_runner, language_version):  # pragma: windows no cover
 
 
 def install_environment(
-        repo_cmd_runner, version, additional_dependencies,
+        prefix, version, additional_dependencies,
 ):  # pragma: windows no cover
     additional_dependencies = tuple(additional_dependencies)
-    assert repo_cmd_runner.exists('package.json')
+    assert prefix.exists('package.json')
     directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
 
-    env_dir = repo_cmd_runner.path(directory)
+    env_dir = prefix.path(directory)
     with clean_path_on_failure(env_dir):
-        cmd = [
-            sys.executable, '-m', 'nodeenv', '--prebuilt',
-            '{{prefix}}{}'.format(directory),
-        ]
-
+        cmd = [sys.executable, '-m', 'nodeenv', '--prebuilt', env_dir]
         if version != 'default':
             cmd.extend(['-n', version])
+        cmd_output(*cmd)
 
-        repo_cmd_runner.run(cmd)
-
-        with in_env(repo_cmd_runner, version):
+        with in_env(prefix, version):
             helpers.run_setup_cmd(
-                repo_cmd_runner,
+                prefix,
                 ('npm', 'install', '-g', '.') + additional_dependencies,
             )
 
 
-def run_hook(repo_cmd_runner, hook, file_args):  # pragma: windows no cover
-    with in_env(repo_cmd_runner, hook['language_version']):
+def run_hook(prefix, hook, file_args):  # pragma: windows no cover
+    with in_env(prefix, hook['language_version']):
         return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/languages/pcre.py b/pre_commit/languages/pcre.py
index eaacc110..fb078ab7 100644
--- a/pre_commit/languages/pcre.py
+++ b/pre_commit/languages/pcre.py
@@ -13,7 +13,7 @@ healthy = helpers.basic_healthy
 install_environment = helpers.no_install
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
+def run_hook(prefix, hook, file_args):
     # For PCRE the entry is the regular expression to match
     cmd = (GREP, '-H', '-n', '-P') + tuple(hook['args']) + (hook['entry'],)
 
diff --git a/pre_commit/languages/pygrep.py b/pre_commit/languages/pygrep.py
index 4914fd66..878f57d0 100644
--- a/pre_commit/languages/pygrep.py
+++ b/pre_commit/languages/pygrep.py
@@ -27,7 +27,7 @@ def _process_filename_by_line(pattern, filename):
     return retv
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
+def run_hook(prefix, hook, file_args):
     exe = (sys.executable, '-m', __name__)
     exe += tuple(hook['args']) + (hook['entry'],)
     return xargs(exe, file_args)
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
index 8d891aa3..7fc5443e 100644
--- a/pre_commit/languages/python.py
+++ b/pre_commit/languages/python.py
@@ -33,8 +33,8 @@ def get_env_patch(venv):
 
 
 @contextlib.contextmanager
-def in_env(repo_cmd_runner, language_version):
-    envdir = repo_cmd_runner.path(
+def in_env(prefix, language_version):
+    envdir = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, language_version),
     )
     with envcontext(get_env_patch(envdir)):
@@ -98,8 +98,8 @@ def get_default_version():
         return get_default_version()
 
 
-def healthy(repo_cmd_runner, language_version):
-    with in_env(repo_cmd_runner, language_version):
+def healthy(prefix, language_version):
+    with in_env(prefix, language_version):
         retcode, _, _ = cmd_output(
             'python', '-c', 'import ctypes, datetime, io, os, ssl, weakref',
             retcode=None,
@@ -127,29 +127,26 @@ def norm_version(version):
     return os.path.expanduser(version)
 
 
-def install_environment(repo_cmd_runner, version, additional_dependencies):
+def install_environment(prefix, version, additional_dependencies):
     additional_dependencies = tuple(additional_dependencies)
     directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
 
     # Install a virtualenv
-    with clean_path_on_failure(repo_cmd_runner.path(directory)):
-        venv_cmd = [
-            sys.executable, '-m', 'virtualenv',
-            '{{prefix}}{}'.format(directory),
-        ]
+    env_dir = prefix.path(directory)
+    with clean_path_on_failure(env_dir):
+        venv_cmd = [sys.executable, '-m', 'virtualenv', env_dir]
         if version != 'default':
             venv_cmd.extend(['-p', norm_version(version)])
         else:
             venv_cmd.extend(['-p', os.path.realpath(sys.executable)])
         venv_env = dict(os.environ, VIRTUALENV_NO_DOWNLOAD='1')
-        repo_cmd_runner.run(venv_cmd, cwd='/', env=venv_env)
-        with in_env(repo_cmd_runner, version):
+        cmd_output(*venv_cmd, cwd='/', env=venv_env)
+        with in_env(prefix, version):
             helpers.run_setup_cmd(
-                repo_cmd_runner,
-                ('pip', 'install', '.') + additional_dependencies,
+                prefix, ('pip', 'install', '.') + additional_dependencies,
             )
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
-    with in_env(repo_cmd_runner, hook['language_version']):
+def run_hook(prefix, hook, file_args):
+    with in_env(prefix, hook['language_version']):
         return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/languages/ruby.py b/pre_commit/languages/ruby.py
index e7e0c328..3bd7130d 100644
--- a/pre_commit/languages/ruby.py
+++ b/pre_commit/languages/ruby.py
@@ -39,36 +39,32 @@ def get_env_patch(venv, language_version):  # pragma: windows no cover
 
 
 @contextlib.contextmanager
-def in_env(repo_cmd_runner, language_version):  # pragma: windows no cover
-    envdir = repo_cmd_runner.path(
+def in_env(prefix, language_version):  # pragma: windows no cover
+    envdir = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, language_version),
     )
     with envcontext(get_env_patch(envdir, language_version)):
         yield
 
 
-def _install_rbenv(
-        repo_cmd_runner, version='default',
-):  # pragma: windows no cover
+def _install_rbenv(prefix, version='default'):  # pragma: windows no cover
     directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
 
     with tarfile.open(resource_filename('rbenv.tar.gz')) as tf:
-        tf.extractall(repo_cmd_runner.path('.'))
-    shutil.move(
-        repo_cmd_runner.path('rbenv'), repo_cmd_runner.path(directory),
-    )
+        tf.extractall(prefix.path('.'))
+    shutil.move(prefix.path('rbenv'), prefix.path(directory))
 
     # Only install ruby-build if the version is specified
     if version != 'default':
         # ruby-download
         with tarfile.open(resource_filename('ruby-download.tar.gz')) as tf:
-            tf.extractall(repo_cmd_runner.path(directory, 'plugins'))
+            tf.extractall(prefix.path(directory, 'plugins'))
 
         # ruby-build
         with tarfile.open(resource_filename('ruby-build.tar.gz')) as tf:
-            tf.extractall(repo_cmd_runner.path(directory, 'plugins'))
+            tf.extractall(prefix.path(directory, 'plugins'))
 
-    activate_path = repo_cmd_runner.path(directory, 'bin', 'activate')
+    activate_path = prefix.path(directory, 'bin', 'activate')
     with io.open(activate_path, 'w') as activate_file:
         # This is similar to how you would install rbenv to your home directory
         # However we do a couple things to make the executables exposed and
@@ -84,7 +80,7 @@ def _install_rbenv(
             # directory
             "export GEM_HOME='{directory}/gems'\n"
             'export PATH="$GEM_HOME/bin:$PATH"\n'
-            '\n'.format(directory=repo_cmd_runner.path(directory)),
+            '\n'.format(directory=prefix.path(directory)),
         )
 
         # If we aren't using the system ruby, add a version here
@@ -101,35 +97,32 @@ def _install_ruby(runner, version):  # pragma: windows no cover
 
 
 def install_environment(
-        repo_cmd_runner, version, additional_dependencies,
+        prefix, version, additional_dependencies,
 ):  # pragma: windows no cover
     additional_dependencies = tuple(additional_dependencies)
     directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
-    with clean_path_on_failure(repo_cmd_runner.path(directory)):
+    with clean_path_on_failure(prefix.path(directory)):
         # TODO: this currently will fail if there's no version specified and
         # there's no system ruby installed.  Is this ok?
-        _install_rbenv(repo_cmd_runner, version=version)
-        with in_env(repo_cmd_runner, version):
+        _install_rbenv(prefix, version=version)
+        with in_env(prefix, version):
             # Need to call this before installing so rbenv's directories are
             # set up
-            helpers.run_setup_cmd(repo_cmd_runner, ('rbenv', 'init', '-'))
+            helpers.run_setup_cmd(prefix, ('rbenv', 'init', '-'))
             if version != 'default':
-                _install_ruby(repo_cmd_runner, version)
+                _install_ruby(prefix, version)
             # Need to call this after installing to set up the shims
-            helpers.run_setup_cmd(repo_cmd_runner, ('rbenv', 'rehash'))
+            helpers.run_setup_cmd(prefix, ('rbenv', 'rehash'))
             helpers.run_setup_cmd(
-                repo_cmd_runner,
-                ('gem', 'build') + repo_cmd_runner.star('.gemspec'),
+                prefix, ('gem', 'build') + prefix.star('.gemspec'),
             )
             helpers.run_setup_cmd(
-                repo_cmd_runner,
-                (
-                    ('gem', 'install', '--no-ri', '--no-rdoc') +
-                    repo_cmd_runner.star('.gem') + additional_dependencies
-                ),
+                prefix,
+                ('gem', 'install', '--no-ri', '--no-rdoc') +
+                prefix.star('.gem') + additional_dependencies,
             )
 
 
-def run_hook(repo_cmd_runner, hook, file_args):  # pragma: windows no cover
-    with in_env(repo_cmd_runner, hook['language_version']):
+def run_hook(prefix, hook, file_args):  # pragma: windows no cover
+    with in_env(prefix, hook['language_version']):
         return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/languages/script.py b/pre_commit/languages/script.py
index 8c3b0c56..8186e77a 100644
--- a/pre_commit/languages/script.py
+++ b/pre_commit/languages/script.py
@@ -10,7 +10,7 @@ healthy = helpers.basic_healthy
 install_environment = helpers.no_install
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
+def run_hook(prefix, hook, file_args):
     cmd = helpers.to_cmd(hook)
-    cmd = (repo_cmd_runner.prefix_dir + cmd[0],) + cmd[1:]
+    cmd = (prefix.prefix_dir + cmd[0],) + cmd[1:]
     return xargs(cmd, file_args)
diff --git a/pre_commit/languages/swift.py b/pre_commit/languages/swift.py
index f4d1eb5a..2863fbee 100644
--- a/pre_commit/languages/swift.py
+++ b/pre_commit/languages/swift.py
@@ -7,6 +7,7 @@ from pre_commit.envcontext import envcontext
 from pre_commit.envcontext import Var
 from pre_commit.languages import helpers
 from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output
 from pre_commit.xargs import xargs
 
 ENVIRONMENT_DIR = 'swift_env'
@@ -22,8 +23,8 @@ def get_env_patch(venv):  # pragma: windows no cover
 
 
 @contextlib.contextmanager
-def in_env(repo_cmd_runner):  # pragma: windows no cover
-    envdir = repo_cmd_runner.path(
+def in_env(prefix):  # pragma: windows no cover
+    envdir = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
     )
     with envcontext(get_env_patch(envdir)):
@@ -31,25 +32,25 @@ def in_env(repo_cmd_runner):  # pragma: windows no cover
 
 
 def install_environment(
-        repo_cmd_runner, version, additional_dependencies,
+        prefix, version, additional_dependencies,
 ):  # pragma: windows no cover
     helpers.assert_version_default('swift', version)
     helpers.assert_no_additional_deps('swift', additional_dependencies)
-    directory = repo_cmd_runner.path(
+    directory = prefix.path(
         helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
     )
 
     # Build the swift package
     with clean_path_on_failure(directory):
         os.mkdir(directory)
-        repo_cmd_runner.run((
+        cmd_output(
             'swift', 'build',
-            '-C', '{prefix}',
+            '-C', prefix.prefix_dir,
             '-c', BUILD_CONFIG,
             '--build-path', os.path.join(directory, BUILD_DIR),
-        ))
+        )
 
 
-def run_hook(repo_cmd_runner, hook, file_args):  # pragma: windows no cover
-    with in_env(repo_cmd_runner):
+def run_hook(prefix, hook, file_args):  # pragma: windows no cover
+    with in_env(prefix):
         return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/languages/system.py b/pre_commit/languages/system.py
index 693a1601..84cd1fe4 100644
--- a/pre_commit/languages/system.py
+++ b/pre_commit/languages/system.py
@@ -10,5 +10,5 @@ healthy = helpers.basic_healthy
 install_environment = helpers.no_install
 
 
-def run_hook(repo_cmd_runner, hook, file_args):
+def run_hook(prefix, hook, file_args):
     return xargs(helpers.to_cmd(hook), file_args)
diff --git a/pre_commit/prefix.py b/pre_commit/prefix.py
new file mode 100644
index 00000000..128bd861
--- /dev/null
+++ b/pre_commit/prefix.py
@@ -0,0 +1,20 @@
+from __future__ import unicode_literals
+
+import os.path
+
+
+class Prefix(object):
+    def __init__(self, prefix_dir):
+        self.prefix_dir = prefix_dir.rstrip(os.sep) + os.sep
+
+    def path(self, *parts):
+        path = os.path.join(self.prefix_dir, *parts)
+        return os.path.normpath(path)
+
+    def exists(self, *parts):
+        return os.path.exists(self.path(*parts))
+
+    def star(self, end):
+        return tuple(
+            path for path in os.listdir(self.prefix_dir) if path.endswith(end)
+        )
diff --git a/pre_commit/prefixed_command_runner.py b/pre_commit/prefixed_command_runner.py
deleted file mode 100644
index c2de526b..00000000
--- a/pre_commit/prefixed_command_runner.py
+++ /dev/null
@@ -1,50 +0,0 @@
-from __future__ import unicode_literals
-
-import os.path
-import subprocess
-
-from pre_commit.util import cmd_output
-
-
-class PrefixedCommandRunner(object):
-    """A PrefixedCommandRunner allows you to run subprocess commands with
-    comand substitution.
-
-    For instance:
-        PrefixedCommandRunner('/tmp/foo').run(['{prefix}foo.sh', 'bar', 'baz'])
-
-    will run ['/tmp/foo/foo.sh', 'bar', 'baz']
-    """
-
-    def __init__(
-            self,
-            prefix_dir,
-            popen=subprocess.Popen,
-            makedirs=os.makedirs,
-    ):
-        self.prefix_dir = prefix_dir.rstrip(os.sep) + os.sep
-        self.__popen = popen
-        self.__makedirs = makedirs
-
-    def _create_path_if_not_exists(self):
-        if not os.path.exists(self.prefix_dir):
-            self.__makedirs(self.prefix_dir)
-
-    def run(self, cmd, **kwargs):
-        self._create_path_if_not_exists()
-        replaced_cmd = [
-            part.replace('{prefix}', self.prefix_dir) for part in cmd
-        ]
-        return cmd_output(*replaced_cmd, __popen=self.__popen, **kwargs)
-
-    def path(self, *parts):
-        path = os.path.join(self.prefix_dir, *parts)
-        return os.path.normpath(path)
-
-    def exists(self, *parts):
-        return os.path.exists(self.path(*parts))
-
-    def star(self, end):
-        return tuple(
-            path for path in os.listdir(self.prefix_dir) if path.endswith(end)
-        )
diff --git a/pre_commit/repository.py b/pre_commit/repository.py
index 5c11921c..e01b3d1d 100644
--- a/pre_commit/repository.py
+++ b/pre_commit/repository.py
@@ -21,7 +21,7 @@ from pre_commit.clientlib import load_manifest
 from pre_commit.clientlib import MANIFEST_HOOK_DICT
 from pre_commit.languages.all import languages
 from pre_commit.languages.helpers import environment_dir
-from pre_commit.prefixed_command_runner import PrefixedCommandRunner
+from pre_commit.prefix import Prefix
 from pre_commit.schema import apply_defaults
 from pre_commit.schema import validate
 
@@ -33,22 +33,22 @@ def _state(additional_deps):
     return {'additional_dependencies': sorted(additional_deps)}
 
 
-def _state_filename(cmd_runner, venv):
-    return cmd_runner.path(
+def _state_filename(prefix, venv):
+    return prefix.path(
         venv, '.install_state_v' + C.INSTALLED_STATE_VERSION,
     )
 
 
-def _read_state(cmd_runner, venv):
-    filename = _state_filename(cmd_runner, venv)
+def _read_state(prefix, venv):
+    filename = _state_filename(prefix, venv)
     if not os.path.exists(filename):
         return None
     else:
         return json.loads(io.open(filename).read())
 
 
-def _write_state(cmd_runner, venv, state):
-    state_filename = _state_filename(cmd_runner, venv)
+def _write_state(prefix, venv, state):
+    state_filename = _state_filename(prefix, venv)
     staging = state_filename + 'staging'
     with io.open(staging, 'w') as state_file:
         state_file.write(five.to_text(json.dumps(state)))
@@ -56,24 +56,24 @@ def _write_state(cmd_runner, venv, state):
     os.rename(staging, state_filename)
 
 
-def _installed(cmd_runner, language_name, language_version, additional_deps):
+def _installed(prefix, language_name, language_version, additional_deps):
     language = languages[language_name]
     venv = environment_dir(language.ENVIRONMENT_DIR, language_version)
     return (
         venv is None or (
-            _read_state(cmd_runner, venv) == _state(additional_deps) and
-            language.healthy(cmd_runner, language_version)
+            _read_state(prefix, venv) == _state(additional_deps) and
+            language.healthy(prefix, language_version)
         )
     )
 
 
 def _install_all(venvs, repo_url, store):
-    """Tuple of (cmd_runner, language, version, deps)"""
+    """Tuple of (prefix, language, version, deps)"""
     def _need_installed():
         return tuple(
-            (cmd_runner, language_name, version, deps)
-            for cmd_runner, language_name, version, deps in venvs
-            if not _installed(cmd_runner, language_name, version, deps)
+            (prefix, language_name, version, deps)
+            for prefix, language_name, version, deps in venvs
+            if not _installed(prefix, language_name, version, deps)
         )
 
     if not _need_installed():
@@ -90,19 +90,19 @@ def _install_all(venvs, repo_url, store):
         logger.info('Once installed this environment will be reused.')
         logger.info('This may take a few minutes...')
 
-        for cmd_runner, language_name, version, deps in need_installed:
+        for prefix, language_name, version, deps in need_installed:
             language = languages[language_name]
             venv = environment_dir(language.ENVIRONMENT_DIR, version)
 
             # There's potentially incomplete cleanup from previous runs
             # Clean it up!
-            if cmd_runner.exists(venv):
-                shutil.rmtree(cmd_runner.path(venv))
+            if prefix.exists(venv):
+                shutil.rmtree(prefix.path(venv))
 
-            language.install_environment(cmd_runner, version, deps)
+            language.install_environment(prefix, version, deps)
             # Write our state to indicate we're installed
             state = _state(deps)
-            _write_state(cmd_runner, venv, state)
+            _write_state(prefix, venv, state)
 
 
 def _hook(*hook_dicts):
@@ -156,11 +156,11 @@ class Repository(object):
         )
 
     @cached_property
-    def _cmd_runner(self):
-        return PrefixedCommandRunner(self._repo_path)
+    def _prefix(self):
+        return Prefix(self._repo_path)
 
-    def _cmd_runner_from_deps(self, language_name, deps):
-        return self._cmd_runner
+    def _prefix_from_deps(self, language_name, deps):
+        return self._prefix
 
     @cached_property
     def manifest_hooks(self):
@@ -194,7 +194,7 @@ class Repository(object):
             )
         ret = []
         for (language, version), deps in deps_dict.items():
-            ret.append((self._cmd_runner, language, version, deps))
+            ret.append((self._prefix, language, version, deps))
         return tuple(ret)
 
     def require_installed(self):
@@ -211,20 +211,20 @@ class Repository(object):
         self.require_installed()
         language_name = hook['language']
         deps = hook['additional_dependencies']
-        cmd_runner = self._cmd_runner_from_deps(language_name, deps)
-        return languages[language_name].run_hook(cmd_runner, hook, file_args)
+        prefix = self._prefix_from_deps(language_name, deps)
+        return languages[language_name].run_hook(prefix, hook, file_args)
 
 
 class LocalRepository(Repository):
-    def _cmd_runner_from_deps(self, language_name, deps):
-        """local repositories have a cmd runner per hook"""
+    def _prefix_from_deps(self, language_name, deps):
+        """local repositories have a prefix per hook"""
         language = languages[language_name]
         # pcre / pygrep / script / system / docker_image do not have
         # environments so they work out of the current directory
         if language.ENVIRONMENT_DIR is None:
-            return PrefixedCommandRunner(git.get_root())
+            return Prefix(git.get_root())
         else:
-            return PrefixedCommandRunner(self.store.make_local(deps))
+            return Prefix(self.store.make_local(deps))
 
     @cached_property
     def manifest(self):
@@ -245,7 +245,7 @@ class LocalRepository(Repository):
             version = hook['language_version']
             deps = hook['additional_dependencies']
             ret.append((
-                self._cmd_runner_from_deps(language, deps),
+                self._prefix_from_deps(language, deps),
                 language, version, deps,
             ))
         return tuple(ret)
diff --git a/tests/conftest.py b/tests/conftest.py
index 36743d88..fe710e65 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -14,7 +14,6 @@ import six
 import pre_commit.constants as C
 from pre_commit import output
 from pre_commit.logging_handler import add_logging_handler
-from pre_commit.prefixed_command_runner import PrefixedCommandRunner
 from pre_commit.runner import Runner
 from pre_commit.store import Store
 from pre_commit.util import cmd_output
@@ -155,11 +154,6 @@ def store(tempdir_factory):
     yield Store(os.path.join(tempdir_factory.get(), '.pre-commit'))
 
 
-@pytest.yield_fixture
-def cmd_runner(tempdir_factory):
-    yield PrefixedCommandRunner(tempdir_factory.get())
-
-
 @pytest.yield_fixture
 def runner_with_mocked_store(mock_out_store_directory):
     yield Runner('/', C.CONFIG_FILE)
diff --git a/tests/languages/all_test.py b/tests/languages/all_test.py
index 95cec104..6e3ab662 100644
--- a/tests/languages/all_test.py
+++ b/tests/languages/all_test.py
@@ -11,7 +11,7 @@ from pre_commit.languages.all import languages
 @pytest.mark.parametrize('language', all_languages)
 def test_install_environment_argspec(language):
     expected_argspec = inspect.ArgSpec(
-        args=['repo_cmd_runner', 'version', 'additional_dependencies'],
+        args=['prefix', 'version', 'additional_dependencies'],
         varargs=None, keywords=None, defaults=None,
     )
     argspec = inspect.getargspec(languages[language].install_environment)
@@ -26,7 +26,7 @@ def test_ENVIRONMENT_DIR(language):
 @pytest.mark.parametrize('language', all_languages)
 def test_run_hook_argpsec(language):
     expected_argspec = inspect.ArgSpec(
-        args=['repo_cmd_runner', 'hook', 'file_args'],
+        args=['prefix', 'hook', 'file_args'],
         varargs=None, keywords=None, defaults=None,
     )
     argspec = inspect.getargspec(languages[language].run_hook)
@@ -45,7 +45,7 @@ def test_get_default_version_argspec(language):
 @pytest.mark.parametrize('language', all_languages)
 def test_healthy_argspec(language):
     expected_argspec = inspect.ArgSpec(
-        args=['repo_cmd_runner', 'language_version'],
+        args=['prefix', 'language_version'],
         varargs=None, keywords=None, defaults=None,
     )
     argspec = inspect.getargspec(languages[language].healthy)
diff --git a/tests/languages/ruby_test.py b/tests/languages/ruby_test.py
index 1eddea1d..bcaf0986 100644
--- a/tests/languages/ruby_test.py
+++ b/tests/languages/ruby_test.py
@@ -1,39 +1,42 @@
 from __future__ import unicode_literals
 
 import os.path
+import pipes
 
 from pre_commit.languages.ruby import _install_rbenv
+from pre_commit.prefix import Prefix
+from pre_commit.util import cmd_output
 from testing.util import xfailif_windows_no_ruby
 
 
 @xfailif_windows_no_ruby
-def test_install_rbenv(cmd_runner):
-    _install_rbenv(cmd_runner)
+def test_install_rbenv(tempdir_factory):
+    prefix = Prefix(tempdir_factory.get())
+    _install_rbenv(prefix)
     # Should have created rbenv directory
-    assert os.path.exists(cmd_runner.path('rbenv-default'))
+    assert os.path.exists(prefix.path('rbenv-default'))
     # We should have created our `activate` script
-    activate_path = cmd_runner.path('rbenv-default', 'bin', 'activate')
+    activate_path = prefix.path('rbenv-default', 'bin', 'activate')
     assert os.path.exists(activate_path)
 
     # Should be able to activate using our script and access rbenv
-    cmd_runner.run(
-        [
-            'bash',
-            '-c',
-            ". '{prefix}rbenv-default/bin/activate' && rbenv --help",
-        ],
+    cmd_output(
+        'bash', '-c',
+        '. {} && rbenv --help'.format(pipes.quote(prefix.path(
+            'rbenv-default', 'bin', 'activate',
+        ))),
     )
 
 
 @xfailif_windows_no_ruby
-def test_install_rbenv_with_version(cmd_runner):
-    _install_rbenv(cmd_runner, version='1.9.3p547')
+def test_install_rbenv_with_version(tempdir_factory):
+    prefix = Prefix(tempdir_factory.get())
+    _install_rbenv(prefix, version='1.9.3p547')
 
     # Should be able to activate and use rbenv install
-    cmd_runner.run(
-        [
-            'bash',
-            '-c',
-            ". '{prefix}rbenv-1.9.3p547/bin/activate' && rbenv install --help",
-        ],
+    cmd_output(
+        'bash', '-c',
+        '. {} && rbenv install --help'.format(pipes.quote(prefix.path(
+            'rbenv-1.9.3p547', 'bin', 'activate',
+        ))),
     )
diff --git a/tests/prefix_test.py b/tests/prefix_test.py
new file mode 100644
index 00000000..05f3f8a4
--- /dev/null
+++ b/tests/prefix_test.py
@@ -0,0 +1,57 @@
+from __future__ import unicode_literals
+
+import os
+
+import pytest
+
+from pre_commit.prefix import Prefix
+
+
+def norm_slash(*args):
+    return tuple(x.replace('/', os.sep) for x in args)
+
+
+@pytest.mark.parametrize(
+    ('input', 'expected_prefix'), (
+        norm_slash('.', './'),
+        norm_slash('foo', 'foo/'),
+        norm_slash('bar/', 'bar/'),
+        norm_slash('foo/bar', 'foo/bar/'),
+        norm_slash('foo/bar/', 'foo/bar/'),
+    ),
+)
+def test_init_normalizes_path_endings(input, expected_prefix):
+    instance = Prefix(input)
+    assert instance.prefix_dir == expected_prefix
+
+
+PATH_TESTS = (
+    norm_slash('foo', '', 'foo'),
+    norm_slash('foo', 'bar', 'foo/bar'),
+    norm_slash('foo/bar', '../baz', 'foo/baz'),
+    norm_slash('./', 'bar', 'bar'),
+    norm_slash('./', '', '.'),
+    norm_slash('/tmp/foo', '/tmp/bar', '/tmp/bar'),
+)
+
+
+@pytest.mark.parametrize(('prefix', 'path_end', 'expected_output'), PATH_TESTS)
+def test_path(prefix, path_end, expected_output):
+    instance = Prefix(prefix)
+    ret = instance.path(path_end)
+    assert ret == expected_output
+
+
+def test_path_multiple_args():
+    instance = Prefix('foo')
+    ret = instance.path('bar', 'baz')
+    assert ret == os.path.join('foo', 'bar', 'baz')
+
+
+def test_exists_does_not_exist(tmpdir):
+    assert not Prefix(str(tmpdir)).exists('foo')
+
+
+def test_exists_does_exist(tmpdir):
+    tmpdir.ensure('foo')
+    assert Prefix(str(tmpdir)).exists('foo')
diff --git a/tests/prefixed_command_runner_test.py b/tests/prefixed_command_runner_test.py
deleted file mode 100644
index c928dc8a..00000000
--- a/tests/prefixed_command_runner_test.py
+++ /dev/null
@@ -1,133 +0,0 @@
-from __future__ import unicode_literals
-
-import os
-import subprocess
-
-import mock
-import pytest
-
-from pre_commit.prefixed_command_runner import PrefixedCommandRunner
-from pre_commit.util import CalledProcessError
-
-
-def norm_slash(input_tup):
-    return tuple(x.replace('/', os.sep) for x in input_tup)
-
-
-def test_CalledProcessError_str():
-    error = CalledProcessError(
-        1, [str('git'), str('status')], 0, (str('stdout'), str('stderr')),
-    )
-    assert str(error) == (
-        "Command: ['git', 'status']\n"
-        "Return code: 1\n"
-        "Expected return code: 0\n"
-        "Output: \n"
-        "    stdout\n"
-        "Errors: \n"
-        "    stderr\n"
-    )
-
-
-def test_CalledProcessError_str_nooutput():
-    error = CalledProcessError(
-        1, [str('git'), str('status')], 0, (str(''), str('')),
-    )
-    assert str(error) == (
-        "Command: ['git', 'status']\n"
-        "Return code: 1\n"
-        "Expected return code: 0\n"
-        "Output: (none)\n"
-        "Errors: (none)\n"
-    )
-
-
-@pytest.fixture
-def popen_mock():
-    popen = mock.Mock(spec=subprocess.Popen)
-    popen.return_value.communicate.return_value = (b'stdout', b'stderr')
-    return popen
-
-
-@pytest.fixture
-def makedirs_mock():
-    return mock.Mock(spec=os.makedirs)
-
-
-@pytest.mark.parametrize(
-    ('input', 'expected_prefix'), (
-        norm_slash(('.', './')),
-        norm_slash(('foo', 'foo/')),
-        norm_slash(('bar/', 'bar/')),
-        norm_slash(('foo/bar', 'foo/bar/')),
-        norm_slash(('foo/bar/', 'foo/bar/')),
-    ),
-)
-def test_init_normalizes_path_endings(input, expected_prefix):
-    input = input.replace('/', os.sep)
-    expected_prefix = expected_prefix.replace('/', os.sep)
-    instance = PrefixedCommandRunner(input)
-    assert instance.prefix_dir == expected_prefix
-
-
-def test_run_substitutes_prefix(popen_mock, makedirs_mock):
-    instance = PrefixedCommandRunner(
-        'prefix', popen=popen_mock, makedirs=makedirs_mock,
-    )
-    ret = instance.run(['{prefix}bar', 'baz'], retcode=None)
-    popen_mock.assert_called_once_with(
-        (str(os.path.join('prefix', 'bar')), str('baz')),
-        env=None,
-        stdin=subprocess.PIPE,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE,
-    )
-    assert ret == (popen_mock.return_value.returncode, 'stdout', 'stderr')
-
-
-PATH_TESTS = (
-    norm_slash(('foo', '', 'foo')),
-    norm_slash(('foo', 'bar', 'foo/bar')),
-    norm_slash(('foo/bar', '../baz', 'foo/baz')),
-    norm_slash(('./', 'bar', 'bar')),
-    norm_slash(('./', '', '.')),
-    norm_slash(('/tmp/foo', '/tmp/bar', '/tmp/bar')),
-)
-
-
-@pytest.mark.parametrize(('prefix', 'path_end', 'expected_output'), PATH_TESTS)
-def test_path(prefix, path_end, expected_output):
-    instance = PrefixedCommandRunner(prefix)
-    ret = instance.path(path_end)
-    assert ret == expected_output
-
-
-def test_path_multiple_args():
-    instance = PrefixedCommandRunner('foo')
-    ret = instance.path('bar', 'baz')
-    assert ret == os.path.join('foo', 'bar', 'baz')
-
-
-def test_create_path_if_not_exists(in_tmpdir):
-    instance = PrefixedCommandRunner('foo')
-    assert not os.path.exists('foo')
-    instance._create_path_if_not_exists()
-    assert os.path.exists('foo')
-
-
-def test_exists_does_not_exist(in_tmpdir):
-    assert not PrefixedCommandRunner('.').exists('foo')
-
-
-def test_exists_does_exist(in_tmpdir):
-    os.mkdir('foo')
-    assert PrefixedCommandRunner('.').exists('foo')
-
-
-def test_raises_on_error(popen_mock, makedirs_mock):
-    popen_mock.return_value.returncode = 1
-    with pytest.raises(CalledProcessError):
-        instance = PrefixedCommandRunner(
-            '.', popen=popen_mock, makedirs=makedirs_mock,
-        )
-        instance.run(['echo'])
diff --git a/tests/repository_test.py b/tests/repository_test.py
index 1d38d246..1c518eba 100644
--- a/tests/repository_test.py
+++ b/tests/repository_test.py
@@ -191,7 +191,7 @@ def test_run_a_docker_image_hook(tempdir_factory, store, hook_id):
 def test_run_a_node_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'node_hooks_repo',
-        'foo', ['/dev/null'], b'Hello World\n',
+        'foo', [os.devnull], b'Hello World\n',
     )
 
 
@@ -200,7 +200,7 @@ def test_run_a_node_hook(tempdir_factory, store):
 def test_run_versioned_node_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'node_0_11_8_hooks_repo',
-        'node-11-8-hook', ['/dev/null'], b'v0.11.8\nHello World\n',
+        'node-11-8-hook', [os.devnull], b'v0.11.8\nHello World\n',
     )
 
 
@@ -209,7 +209,7 @@ def test_run_versioned_node_hook(tempdir_factory, store):
 def test_run_a_ruby_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'ruby_hooks_repo',
-        'ruby_hook', ['/dev/null'], b'Hello world from a ruby hook\n',
+        'ruby_hook', [os.devnull], b'Hello world from a ruby hook\n',
     )
 
 
@@ -219,7 +219,7 @@ def test_run_versioned_ruby_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'ruby_versioned_hooks_repo',
         'ruby_hook',
-        ['/dev/null'],
+        [os.devnull],
         b'2.1.5\nHello world from a ruby hook\n',
     )
 
@@ -242,7 +242,7 @@ def test_run_ruby_hook_with_disable_shared_gems(
         _test_hook_repo(
             tempdir_factory, store, 'ruby_versioned_hooks_repo',
             'ruby_hook',
-            ['/dev/null'],
+            [os.devnull],
             b'2.1.5\nHello world from a ruby hook\n',
         )
 
@@ -251,7 +251,7 @@ def test_run_ruby_hook_with_disable_shared_gems(
 def test_system_hook_with_spaces(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'system_hook_with_spaces_repo',
-        'system-hook-with-spaces', ['/dev/null'], b'Hello World\n',
+        'system-hook-with-spaces', [os.devnull], b'Hello World\n',
     )
 
 
@@ -276,7 +276,7 @@ def test_golang_hook(tempdir_factory, store):
 def test_missing_executable(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'not_found_exe',
-        'not-found-exe', ['/dev/null'],
+        'not-found-exe', [os.devnull],
         b'Executable `i-dont-exist-lol` not found',
         expected_return_code=1,
     )
@@ -424,7 +424,7 @@ def test_cwd_of_hook(tempdir_factory, store):
 def test_lots_of_files(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'script_hooks_repo',
-        'bash_hook', ['/dev/null'] * 15000, mock.ANY,
+        'bash_hook', [os.devnull] * 15000, mock.ANY,
     )
 
 
@@ -467,7 +467,7 @@ def test_additional_python_dependencies_installed(tempdir_factory, store):
     config['hooks'][0]['additional_dependencies'] = ['mccabe']
     repo = Repository.create(config, store)
     repo.require_installed()
-    with python.in_env(repo._cmd_runner, 'default'):
+    with python.in_env(repo._prefix, 'default'):
         output = cmd_output('pip', 'freeze', '-l')[1]
         assert 'mccabe' in output
 
@@ -484,7 +484,7 @@ def test_additional_dependencies_roll_forward(tempdir_factory, store):
     repo = Repository.create(config, store)
     repo.require_installed()
     # We should see our additional dependency installed
-    with python.in_env(repo._cmd_runner, 'default'):
+    with python.in_env(repo._prefix, 'default'):
         output = cmd_output('pip', 'freeze', '-l')[1]
         assert 'mccabe' in output
 
@@ -499,7 +499,7 @@ def test_additional_ruby_dependencies_installed(
     config['hooks'][0]['additional_dependencies'] = ['thread_safe', 'tins']
     repo = Repository.create(config, store)
     repo.require_installed()
-    with ruby.in_env(repo._cmd_runner, 'default'):
+    with ruby.in_env(repo._prefix, 'default'):
         output = cmd_output('gem', 'list', '--local')[1]
         assert 'thread_safe' in output
         assert 'tins' in output
@@ -516,7 +516,7 @@ def test_additional_node_dependencies_installed(
     config['hooks'][0]['additional_dependencies'] = ['lodash']
     repo = Repository.create(config, store)
     repo.require_installed()
-    with node.in_env(repo._cmd_runner, 'default'):
+    with node.in_env(repo._prefix, 'default'):
         cmd_output('npm', 'config', 'set', 'global', 'true')
         output = cmd_output('npm', 'ls')[1]
         assert 'lodash' in output
@@ -533,7 +533,7 @@ def test_additional_golang_dependencies_installed(
     config['hooks'][0]['additional_dependencies'] = deps
     repo = Repository.create(config, store)
     repo.require_installed()
-    binaries = os.listdir(repo._cmd_runner.path(
+    binaries = os.listdir(repo._prefix.path(
         helpers.environment_dir(golang.ENVIRONMENT_DIR, 'default'), 'bin',
     ))
     # normalize for windows
@@ -600,7 +600,7 @@ def test_control_c_control_c_on_install(tempdir_factory, store):
 
     # Should have made an environment, however this environment is broken!
     envdir = 'py_env-{}'.format(python.get_default_version())
-    assert repo._cmd_runner.exists(envdir)
+    assert repo._prefix.exists(envdir)
 
     # However, it should be perfectly runnable (reinstall after botched
     # install)
@@ -618,7 +618,7 @@ def test_invalidated_virtualenv(tempdir_factory, store):
     # Simulate breaking of the virtualenv
     repo.require_installed()
     version = python.get_default_version()
-    libdir = repo._cmd_runner.path('py_env-{}'.format(version), 'lib', version)
+    libdir = repo._prefix.path('py_env-{}'.format(version), 'lib', version)
     paths = [
         os.path.join(libdir, p) for p in ('site.py', 'site.pyc', '__pycache__')
     ]
diff --git a/tests/util_test.py b/tests/util_test.py
index ba2b4a82..156148d5 100644
--- a/tests/util_test.py
+++ b/tests/util_test.py
@@ -5,6 +5,7 @@ import random
 
 import pytest
 
+from pre_commit.util import CalledProcessError
 from pre_commit.util import clean_path_on_failure
 from pre_commit.util import cmd_output
 from pre_commit.util import cwd
@@ -12,6 +13,34 @@ from pre_commit.util import memoize_by_cwd
 from pre_commit.util import tmpdir
 
 
+def test_CalledProcessError_str():
+    error = CalledProcessError(
+        1, [str('git'), str('status')], 0, (str('stdout'), str('stderr')),
+    )
+    assert str(error) == (
+        "Command: ['git', 'status']\n"
+        "Return code: 1\n"
+        "Expected return code: 0\n"
+        "Output: \n"
+        "    stdout\n"
+        "Errors: \n"
+        "    stderr\n"
+    )
+
+
+def test_CalledProcessError_str_nooutput():
+    error = CalledProcessError(
+        1, [str('git'), str('status')], 0, (str(''), str('')),
+    )
+    assert str(error) == (
+        "Command: ['git', 'status']\n"
+        "Return code: 1\n"
+        "Expected return code: 0\n"
+        "Output: (none)\n"
+        "Errors: (none)\n"
+    )
+
+
 @pytest.fixture
 def memoized_by_cwd():
     @memoize_by_cwd