Make the CheckTreeIsOpen presubmit check fail on IOError.

presubmit_canned_checks.py

 # Copyright (c) 2012 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 440 matching lines @@
         return [output_api.PresubmitError(short_text, long_text=long_text)]
     else:
       # TODO(bradnelson): drop this once all users are gone.
       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)]
-  except IOError:
-    pass
+  except IOError as e:
+    return [output_api.PresubmitError('Error fetching tree status.',
+                                      long_text=str(e))]
   return []
 
 
 def RunUnitTestsInDirectory(
     input_api, output_api, directory, whitelist=None, blacklist=None):
   """Lists all files in a directory and runs them. Doesn't recurse.
 
   It's mainly a wrapper for RunUnitTests. USe whitelist and blacklist to filter
   tests accordingly.
   """
@@ skipping 440 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