Improve pylint error message with an old version is used.

presubmit_canned_checks.py

 # Copyright (c) 2011 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):
@@ skipping 616 matching lines @@
   import warnings
   warnings.filterwarnings('ignore', category=DeprecationWarning)
   try:
     files = _FetchAllFiles(input_api, white_list, black_list)
     if not files:
       return []
     # Now that at least one python file was modified and all the python files
     # were listed, try to run pylint.
     try:
       from pylint import lint
+      from pylint.utils import UnknownMessage
       input_api.logging.debug(
           'Using pylint v%s from %s' % (lint.version, lint.__file__))
     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'
           'or visit http://pypi.python.org/pypi/setuptools.\n'
           'Cannot do static analysis of python files.')]
 
     def run_lint(files):
       try:
         lint.Run(files)
         assert False
       except SystemExit, e:
         # pylint has the bad habit of calling sys.exit(), trap it here.
         return e.code
+      except UnknownMessage, e:
+        return 'Please upgrade pylint: %s' % e
 
     result = None
     if not input_api.verbose:
       result = run_lint(sorted(files))
     else:
       for filename in sorted(files):
         print('Running pylint on %s' % filename)
-        out = run_lint([filename])
-        if out:
-          result = out
-    if result:
+        result = run_lint([filename]) or result
+    if isinstance(result, basestring):
+      return [error_type(result)]
+    elif result:
       return [error_type('Fix pylint errors first.')]
     return []
   finally:
     warnings.filterwarnings('default', category=DeprecationWarning)
 
 
 # TODO(dpranke): Get the host_url from the input_api instead
 def CheckRietveldTryJobExecution(input_api, output_api, host_url, platforms,
                                  owner):
   if not input_api.is_committing:
@@ skipping 273 matching lines @@
     results.extend(input_api.canned_checks.CheckSvnForCommonMimeTypes(
         input_api, output_api))
     snapshot("checking license")
     results.extend(input_api.canned_checks.CheckLicense(
         input_api, output_api, license_header, source_file_filter=sources))
     snapshot("checking was uploaded")
     results.extend(input_api.canned_checks.CheckChangeWasUploaded(
         input_api, output_api))
   snapshot("done")
   return results