Raise Exception instead of failure when some steps fail.

tools/tests/factory_configuration/expected/Housekeeper-Nightly-DEPSRoll

 {
     'TargetPath': <Object>,
     '_autogen_svn_password_file': '.autogen_svn_password',
     '_autogen_svn_username_file': '.autogen_svn_username',
     '_build_targets': [],
     '_builder_name': 'Housekeeper-Nightly-DEPSRoll',
     '_common_args': [
         '--autogen_svn_baseurl',
         'https://skia-autogen.googlecode.com/svn',
         '--configuration',
@@ skipping 86 matching lines @@
                     '--num_cores',
                     <Object>,
                     '--is_try',
                     'False',
                     '--bench_pictures_cfg',
                     'default',
                 ],
                 'description': 'UpdateScripts',
                 'doStepIf': <Object>,
                 'env': {},
+                'exception_on_failure': <Object>,
                 'flunkOnFailure': <Object>,
                 'get_props_from_stdout': {
                     'buildbot_revision': 'Skiabot scripts updated to (\w+)',
                 },
                 'haltOnFailure': <Object>,
                 'hideStepIf': <Object>,
                 'is_rebaseline_step': <Object>,
                 'is_upload_step': <Object>,
                 'timeout': <Object>,
                 'workdir': 'build',
@@ skipping 35 matching lines @@
                     '--num_cores',
                     <Object>,
                     '--is_try',
                     'False',
                     '--bench_pictures_cfg',
                     'default',
                 ],
                 'description': 'Update',
                 'doStepIf': <Object>,
                 'env': {},
+                'exception_on_failure': <Object>,
                 'flunkOnFailure': <Object>,
                 'get_props_from_stdout': {
                     'chrome_revision': 'Chrome updated to (\w+)',
                     'got_revision': 'Skia updated to (\w+)',
                 },
                 'haltOnFailure': <Object>,
                 'hideStepIf': <Object>,
                 'is_rebaseline_step': <Object>,
                 'is_upload_step': <Object>,
                 'timeout': <Object>,
@@ skipping 36 matching lines @@
                     '--num_cores',
                     <Object>,
                     '--is_try',
                     'False',
                     '--bench_pictures_cfg',
                     'default',
                 ],
                 'description': 'DEPSRoll',
                 'doStepIf': <Object>,
                 'env': {},
+                'exception_on_failure': <Object>,
                 'flunkOnFailure': <Object>,
                 'get_props_from_stdout': {
                     'control_issue': 'Control Issue number: (\d+) ',
                     'deps_roll_issue': 'Deps roll Issue number: (\d+) ',
                 },
                 'haltOnFailure': <Object>,
                 'hideStepIf': <Object>,
                 'is_rebaseline_step': <Object>,
                 'is_upload_step': <Object>,
                 'timeout': <Object>,
                 'workdir': 'build/src',
             },
         ],
     ],
 }