Add error_handler and use it.

pre_commit/error_handler.py

@@ -0,0 +1,42 @@
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import contextlib
+import io
+import os.path
+import traceback
+
+from pre_commit.errors import FatalError
+from pre_commit.store import Store
+
+
+# For testing purposes
+class PreCommitSystemExit(SystemExit):
+    pass
+
+
+def _log_and_exit(msg, exc, formatted, print_fn=print):
+    error_msg = '{0}: {1}: {2}'.format(msg, type(exc).__name__, exc)
+    print_fn(error_msg)
+    print_fn('Check the log at ~/.pre-commit/pre-commit.log')
+    store = Store()
+    store.require_created()
+    with io.open(os.path.join(store.directory, 'pre-commit.log'), 'w') as log:
+        log.write(error_msg + '\n')
+        log.write(formatted + '\n')
+    raise PreCommitSystemExit(1)
+
+
+@contextlib.contextmanager
+def error_handler():
+    try:
+        yield
+    except FatalError as e:
+        _log_and_exit('An error has occurred', e, traceback.format_exc())
+    except Exception as e:
+        _log_and_exit(
+            'An unexpected error has occurred',
+            e,
+            traceback.format_exc(),
+        )

pre_commit/errors.py

@@ -0,0 +1,6 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+
+class FatalError(RuntimeError):
+    pass

pre_commit/five.py

@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-"""five: six, redux"""
 # pylint:disable=invalid-name
 PY2 = str is bytes
 PY3 = str is not bytes

pre_commit/jsonschema_extensions.py

@@ -20,20 +20,20 @@ def extend_validator_cls(validator_cls, modify):
 
 
 def default_values(properties, instance):
-    for property, subschema in properties.items():
+    for prop, subschema in properties.items():
         if 'default' in subschema:
             instance.setdefault(
-                property, copy.deepcopy(subschema['default']),
+                prop, copy.deepcopy(subschema['default']),
             )
 
 
 def remove_default_values(properties, instance):
-    for property, subschema in properties.items():
+    for prop, subschema in properties.items():
         if (
-            'default' in subschema and
-            instance.get(property) == subschema['default']
+                'default' in subschema and
+                instance.get(prop) == subschema['default']
         ):
-            del instance[property]
+            del instance[prop]
 
 
 _AddDefaultsValidator = extend_validator_cls(

pre_commit/main.py

@@ -9,6 +9,7 @@ from pre_commit.commands.clean import clean
 from pre_commit.commands.install_uninstall import install
 from pre_commit.commands.install_uninstall import uninstall
 from pre_commit.commands.run import run
+from pre_commit.error_handler import error_handler
 from pre_commit.runner import Runner
 from pre_commit.util import entry
 
@@ -83,28 +84,29 @@ def main(argv):
         else:
             parser.parse_args(['--help'])
 
-    runner = Runner.create()
+    with error_handler():
+        runner = Runner.create()
 
-    if args.command == 'install':
-        return install(
-            runner, overwrite=args.overwrite, hooks=args.install_hooks,
-        )
-    elif args.command == 'uninstall':
-        return uninstall(runner)
-    elif args.command == 'clean':
-        return clean(runner)
-    elif args.command == 'autoupdate':
-        return autoupdate(runner)
-    elif args.command == 'run':
-        return run(runner, args)
-    else:
-        raise NotImplementedError(
-            'Command {0} not implemented.'.format(args.command)
-        )
+        if args.command == 'install':
+            return install(
+                runner, overwrite=args.overwrite, hooks=args.install_hooks,
+            )
+        elif args.command == 'uninstall':
+            return uninstall(runner)
+        elif args.command == 'clean':
+            return clean(runner)
+        elif args.command == 'autoupdate':
+            return autoupdate(runner)
+        elif args.command == 'run':
+            return run(runner, args)
+        else:
+            raise NotImplementedError(
+                'Command {0} not implemented.'.format(args.command)
+            )
 
-    raise AssertionError(
-        'Command {0} failed to exit with a returncode'.format(args.command)
-    )
+        raise AssertionError(
+            'Command {0} failed to exit with a returncode'.format(args.command)
+        )
 
 
 if __name__ == '__main__':

pre_commit/output.py

@@ -16,13 +16,13 @@ COLS = int(
 
 
 def get_hook_message(
-    start,
-    postfix='',
-    end_msg=None,
-    end_len=0,
-    end_color=None,
-    use_color=None,
-    cols=COLS,
+        start,
+        postfix='',
+        end_msg=None,
+        end_len=0,
+        end_color=None,
+        use_color=None,
+        cols=COLS,
 ):
     """Prints a message for running a hook.