Fix bot_update to correctly handle exceptions

If an exception occurs during a try block which prevents a step from actually executing, then the finally block's attempt to access step.active_result will fail, and the original exception will be hidden behind a new exception from the recipe engine. This CL changes this behavior so that the original exception will always fire.

Review-Url: https://codereview.chromium.org/2175103002

recipe_modules/bot_update/api.py

@@ -231,20 +231,25 @@ class BotUpdateApi(recipe_api.RecipeApi):
       name += ' - %s' % suffix
 
     # Ah hah! Now that everything is in place, lets run bot_update!
+    step_result = None
     try:
       # 87 and 88 are the 'patch failure' codes for patch download and patch
       # apply, respectively. We don't actually use the error codes, and instead
       # rely on emitted json to determine cause of failure.
-      self(name, cmd, step_test_data=step_test_data,
+      step_result = self(name, cmd, step_test_data=step_test_data,
            ok_ret=(0, 87, 88), **kwargs)
+    except self.m.step.StepFailure as f:
+      step_result = f.result
+      raise
     finally:
-      step_result = self.m.step.active_result
+      if step_result:
         self._last_returned_properties = step_result.json.output.get(
             'properties', {})
 
         if update_presentation:
           # Set properties such as got_revision.
-        for prop_name, prop_value in self.last_returned_properties.iteritems():
+          for prop_name, prop_value in (
+              self.last_returned_properties.iteritems()):
             step_result.presentation.properties[prop_name] = prop_value
         # Add helpful step description in the step UI.
         if 'step_text' in step_result.json.output:
@@ -258,7 +263,8 @@ class BotUpdateApi(recipe_api.RecipeApi):
         # Set the "checkout" path for the main solution.
         # This is used by the Chromium module to figure out where to look for
         # the checkout.
-      # If there is a patch failure, emit another step that said things failed.
+        # If there is a patch failure, emit another step that said things
+        # failed.
         if step_result.json.output.get('patch_failure'):
           return_code = step_result.json.output.get('patch_apply_return_code')
           if return_code == 3:
@@ -267,8 +273,8 @@ class BotUpdateApi(recipe_api.RecipeApi):
             self.m.python.inline(
                 'Patch failure',
                 ('import sys;'
-               'print "Patch download failed. See bot_update step for details";'
-               'sys.exit(1)'),
+                 'print "Patch download failed. See bot_update step for'
+                 ' details";sys.exit(1)'),
                 infra_step=True,
                 step_test_data=lambda: self.m.raw_io.test_api.output(
                   'Patch download failed. See bot_update step for details',