Fix node runner for running without a system-level node installed.

pre_commit/languages/helpers.py

@@ -24,7 +24,7 @@ class Environment(object):
         """
         raise NotImplementedError
 
-    def run(self, cmd, stdin=None, **kwargs):
+    def run(self, cmd, stdin=None):
         """Returns (returncode, stdout, stderr)."""
         proc = subprocess.Popen(
             ['bash', '-c', ' '.join([self.env_prefix, cmd])],

pre_commit/languages/node.py

@@ -31,13 +31,12 @@ def install_environment():
     with python.in_env() as python_env:
         python_env.run('pip install nodeenv')
 
-        try:
-            # Try and use the system level node executable first
-            python_env.run('nodeenv -n system {0}'.format(NODE_ENV))
-        except Exception:
-            # TODO: log exception here
-            # cleanup
-            local.path(NODE_ENV).remove()
+        # Try and use the system level node executable first
+        retcode, _, _ = python_env.run('nodeenv -n system {0}'.format(NODE_ENV))
+        # TODO: log failure here
+        # cleanup
+        if retcode:
+            local.path(NODE_ENV).delete()
             python_env.run('nodeenv --jobs 4 {0}'.format(NODE_ENV))
 
         with in_env() as node_env: