Readdress use_counter_feature_enum issue

third_party/WebKit/Source/core/frame/PRESUBMIT.py

 # Copyright 2014 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.
 
 """Blink frame presubmit script
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 56 matching lines @@
     source_path = ''
     for f in input_api.AffectedFiles():
         if f.LocalPath().endswith('UseCounter.h'):
             source_path = f.LocalPath()
             break
     else:
         return []
 
     start_marker = '^enum Feature : uint32_t {'
     end_marker = '^kNumberOfFeatures'
-    should_update_histogram, duplicated_values = update_histogram_enum.HistogramNeedsUpdate(
-        histogram_enum_name='FeatureObserver',
-        source_enum_path=source_path,
-        start_marker=start_marker,
-        end_marker=end_marker,
-        strip_k_prefix=True)
-    if duplicated_values:
+    try:
+        if update_histogram_enum.HistogramNeedsUpdate(
+                histogram_enum_name='FeatureObserver',
+                source_enum_path=source_path,
+                start_marker=start_marker,
+                end_marker=end_marker,
+                strip_k_prefix=True):
+            return [output_api.PresubmitPromptWarning(
+                'UseCounter::Feature has been updated and the UMA mapping needs'
+                'to be regenerated. Please run '
+                'update_use_counter_feature_enum.py in '
+                'src/tools/metrics/histograms/ to update the mapping.',
+                items=[source_path])]
+    except Exception as duplicated_value:   # pylint: disable=W0703

[Ilya Sherman, 2017/04/21 22:51:40]

Please catch only the specific type of exception that's relevant for
duplicated_values, rather than swallowing all exceptions.  (This is also what
the Python warning is warning about.  You should not disable this warning.)

         return [output_api.PresubmitPromptWarning(
             'UseCounter::Feature has been updated and there exists duplicated '
-            'values between (%s) and (%s)' % duplicated_values,
-            items=[source_path])]
-    if should_update_histogram:
-        return [output_api.PresubmitPromptWarning(
-            'UseCounter::Feature has been updated and the UMA mapping needs to '
-            'be regenerated. Please run update_use_counter_feature_enum.py in '
-            'src/tools/metrics/histograms/ to update the mapping.',
+            'values between (%s) and (%s)' % duplicated_value.args,
             items=[source_path])]
 
     return []
 
 
 def CheckChangeOnUpload(input_api, output_api):
     results = []
     results.extend(_RunUseCounterChecks(input_api, output_api))
     results.extend(_RunUmaHistogramChecks(input_api, output_api))
     return results
 
 
 def CheckChangeOnCommit(input_api, output_api):
     results = []
     results.extend(_RunUseCounterChecks(input_api, output_api))
     results.extend(_RunUmaHistogramChecks(input_api, output_api))
     return results