improve logging slightly

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):
@@ skipping 613 matching lines @@
         'Build(s) pending. It is suggested to wait that no more than %d '
             'builds are pending.' % max_pendings,
         long_text='\n'.join(out))]
   return []
 
 
 def CheckOwners(input_api, output_api, source_file_filter=None):
   if not input_api.is_committing:
     return []
   if input_api.tbr:
-    return [output_api.PresubmitNotifyResult('--tbr was specified, '
-                                             'skipping OWNERS check')]
+    return [output_api.PresubmitNotifyResult(
+        '--tbr was specified, skipping OWNERS check')]
   if not input_api.change.issue:
-    return [output_api.PresubmitError('Change not uploaded for review')]
+    return [output_api.PresubmitError(
+        "OWNERS check failed: this change has no Rietveld issue number, so "
+        "we can't check it for approvals.")]
 
   affected_files = set([f.LocalPath() for f in
       input_api.change.AffectedFiles(source_file_filter)])
 
   owners_db = input_api.owners_db
   owner_email, approvers = _RietveldOwnerAndApprovers(input_api,
                                                       owners_db.email_regexp)
   approvers_plus_owner = approvers.union(set([owner_email]))
 
   missing_files = owners_db.files_not_covered_by(affected_files,
@@ skipping 178 matching lines @@
       input_api, output_api, source_file_filter=text_files))
   results.extend(input_api.canned_checks.CheckSvnForCommonMimeTypes(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckLicense(
       input_api, output_api, license_header, source_file_filter=sources))
   results.extend(_CheckConstNSObject(
       input_api, output_api, source_file_filter=sources))
   results.extend(_CheckSingletonInHeaders(
       input_api, output_api, source_file_filter=sources))
   return results