From https://logs.chromium.org/logs/chrome/bb/chromium.perf/Linux_Builder_Perf/34187/+/recipes/steps/Uncaught_Exception/0/logs/exception/0

Traceback (most recent call last):
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/run.py", line 287, in _new_run
    recipe_result = recipe_script.run(api, self.properties, self.environ)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/loader.py", line 108, in run
    self.run_steps, properties, environ, self.PROPERTIES, api=api)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/loader.py", line 636, in invoke_with_properties
    arg_names, **additional_args)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/loader.py", line 599, in _invoke_with_properties
    return callable_obj(*props, **additional_args)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/recipes/chromium.py", line 51, in RunSteps
    api.chromium_tests.main_waterfall_steps()
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/recipe_api.py", line 759, in _inner
    return func(*a, **kw)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/recipe_modules/chromium_tests/api.py", line 927, in main_waterfall_steps
    self.package_build(mastername, buildername, update_step, bot_db)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/recipe_api.py", line 759, in _inner
    return func(*a, **kw)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/recipe_modules/chromium_tests/api.py", line 472, in package_build
    platform=self.m.chromium.c.HOST_PLATFORM
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/.recipe_deps/recipe_engine/recipe_engine/recipe_api.py", line 759, in _inner
    return func(*a, **kw)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/recipe_modules/archive/api.py", line 84, in zip_and_upload_build
    cp_branch, cp_number = self.m.commit_position.parse(commit_position)
  File "/b/rr/tmpZEdEMN/rw/checkout/scripts/slave/recipe_modules/commit_position/api.py", line 17, in parse
    match = cls.RE_COMMIT_POSITION.match(value)
TypeError: expected string or buffer

That's no commit position footer, which is  bug 872722