Add RunPylint as a canned presubmit check.

presubmit_canned_checks.py

 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Generic presubmit checks that can be reused by other presubmit checks."""
 
 ### Description checks
 
 def CheckChangeHasTestField(input_api, output_api):
   """Requires that the changelist have a TEST= field."""
@@ skipping 432 matching lines @@
     # Discard the output if returncode == 0
     if subproc.returncode:
       outputs.append('Test \'%s\' failed with code %d\n%s\n%s\n' % (
           unit_test_name, subproc.returncode, stdoutdata, stderrdata))
   if outputs:
     return [message_type('%d unit tests failed.' % len(outputs),
                                 long_text='\n'.join(outputs))]
   return []
 
 
+def RunPylint(input_api, output_api, source_file_filter=None):
+  """Run pylint on python files."""
+  import warnings
+  # On certain pylint/python version combination, running pylint throws a lot of
+  # warning messages.
+  warnings.filterwarnings('ignore', category=DeprecationWarning)
+  try:
+    if not source_file_filter:
+      source_file_filter = lambda f: f.LocalPath().endswith('.py')
+    files = [f.LocalPath()
+            for f in input_api.AffectedSourceFiles(source_file_filter)]
+    try:
+      from pylint import lint
+      if lint.Run(sorted(files)):
+        return [output_api.PresubmitPromptWarning('Fix pylint errors first.')]
+      return []
+    except ImportError:
+      if input_api.platform == 'win32':
+        return [output_api.PresubmitNotifyResult(
+          'Warning: Can\'t run pylint because it is not installed. Please '
+          'install manually\n'
+          'Cannot do static analysis of python files.')]
+      return [output_api.PresubmitError(
+          'Please install pylint with "sudo apt-get install python-setuptools; '
+          'sudo easy_install pylint"\n'
+          'Cannot do static analysis of python files.')]
+  finally:
+    warnings.filterwarnings('default', category=DeprecationWarning)
+
+
 def CheckRietveldTryJobExecution(input_api, output_api, host_url, platforms,
                                  owner):
   if not input_api.is_committing:
     return []
   if not input_api.change.issue or not input_api.change.patchset:
     return []
   url = '%s/%d/get_build_results/%d' % (
       host_url, input_api.change.issue, input_api.change.patchset)
   try:
     connection = input_api.urllib2.urlopen(url)
@@ skipping 63 matching lines @@
     pending_builds_len = len(builder.get('pending_builds', []))
     if pending_builds_len > max_pendings:
       out.append('%s has %d build(s) pending' %
                   (builder_name, pending_builds_len))
   if out:
     return [output_api.PresubmitPromptWarning(
         'Build(s) pending. It is suggested to wait that no more than %d '
             'builds are pending.' % max_pendings,
         long_text='\n'.join(out))]
   return []