Use more sensible behavior in presubmit checks.

presubmit_canned_checks.py

 #!/usr/bin/env python
 # Copyright (c) 2006-2009 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."""
 
 
 def CheckChangeHasTestField(input_api, output_api):
   """Requires that the changelist have a TEST= field."""
@@ skipping 56 matching lines @@
       CheckDoNotSubmitInFiles(input_api, output_api)
       )
 
 
 def CheckChangeHasNoTabs(input_api, output_api):
   """Checks that there are no tab characters in any of the text files to be
   submitted.
   """
   for f, line_num, line in input_api.RightHandSideLines():
     if '\t' in line:
-      return [output_api.PresubmitError(
+      return [output_api.PresubmitPromptWarning(
           "Found a tab character in %s, line %s" %
           (f.LocalPath(), line_num))]
   return []
 
 
 def CheckLongLines(input_api, output_api, maxlen=80):
   """Checks that there aren't any lines longer than maxlen characters in any of
   the text files to be submitted.
   """
   bad = []
   for f, line_num, line in input_api.RightHandSideLines():
     if len(line) > maxlen:
       bad.append(
           '%s, line %s, %s chars' %
           (f.LocalPath(), line_num, len(line)))
       if len(bad) == 5:  # Just show the first 5 errors.
         break
 
   if bad:
     msg = "Found lines longer than %s characters (first 5 shown)." % maxlen
     return [output_api.PresubmitPromptWarning(msg, items=bad)]
   else:
     return []
 
 
 def CheckTreeIsOpen(input_api, output_api, url, closed):
   """Checks that an url's content doesn't match a regexp that would mean that
   the tree is closed."""
+  assert(input_api.is_committing)
   try:
     connection = input_api.urllib2.urlopen(url)
     status = connection.read()
     connection.close()
     if input_api.re.match(closed, status):
       long_text = status + '\n' + url
-      return [output_api.PresubmitError("The tree is closed.",
-                                        long_text=long_text)]
+      return [output_api.PresubmitPromptWarning("The tree is closed.",
+                                                long_text=long_text)]
   except IOError:
     pass
   return []
 
 
 def _RunPythonUnitTests_LoadTests(input_api, module_name):
   """Meant to be stubbed out during unit testing."""
   module = __import__(module_name)
   for part in module_name.split('.')[1:]:
     module = getattr(module, part)
@@ skipping 14 matching lines @@
     except ImportError:
       outputs.append(message_type("Failed to load %s" % unit_test,
                                   long_text=input_api.traceback.format_exc()))
 
   results = input_api.unittest.TextTestRunner(verbosity=0).run(
       input_api.unittest.TestSuite(tests_suite))
   if not results.wasSuccessful():
     outputs.append(message_type(
         "%d unit tests failed." % (results.failures + results.errors)))
   return outputs