This is a weird python stack trace during an upload-to-google-storage call in CIPD?

Successfully uploaded /b/s/w/ir/cache/chrome_staging/full-build-mac_b95b32d7dd5eda08b565d07fb597a85503ac3d53.zip to gs://chromium-mac-archive/chromium.mac/Mac Builder (dbg)
/b/s/w/ir/cache/vpython/cbb391/bin/python /b/s/w/ir/kitchen-checkout/depot_tools/gsutil.py cp file:///b/s/w/ir/cache/chrome_staging/LAST_CHANGE "gs://chromium-mac-archive/chromium.mac/Mac Builder (dbg)/LAST_CHANGE"
Traceback (most recent call last):
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/zip_build.py", line 569, in <module>
    sys.exit(main(sys.argv))
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/zip_build.py", line 557, in main
    urls = Archive(options)
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/zip_build.py", line 445, in Archive
    options.gsutil_py_path)
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/zip_build.py", line 277, in UploadToGoogleStorage
    override_gsutil=override_gsutil):
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/slave_utils.py", line 384, in GSUtilCopyFile
    add_quiet_flag=add_quiet_flag)
  File "/b/s/w/ir/kitchen-checkout/build/scripts/slave/slave_utils.py", line 340, in GSUtilCopy
    return chromium_utils.RunCommand(command)
  File "/b/s/w/ir/kitchen-checkout/build/scripts/common/chromium_utils.py", line 1026, in RunCommand
    bufsize=0, **kwargs)
  File "/b/s/w/ir/cipd_bin_packages/lib/python2.7/subprocess.py", line 390, in __init__
    errread, errwrite)
  File "/b/s/w/ir/cipd_bin_packages/lib/python2.7/subprocess.py", line 1024, in _execute_child
    child_exception = pickle.loads(data)
  File "/b/s/w/ir/cipd_bin_packages/lib/python2.7/pickle.py", line 1388, in loads
    return Unpickler(file).load()
  File "/b/s/w/ir/cipd_bin_packages/lib/python2.7/pickle.py", line 864, in load
    dispatch[key](self)
  File "/b/s/w/ir/cipd_bin_packages/lib/python2.7/pickle.py", line 977, in load_string
    self.append(rep.decode("string-escape"))
LookupError: unknown encoding: string-escape
step returned non-zero exit code: 1

This is unrelated to CIPD, since CIPD is not used by 'package build' step and cipd_bin_packages appearing in the stack trace is just a location of python on bots.

I'm not sure why this error happened. Most of its mentions on the internet are related to chroots or "frozen" interpreter, which implies it may be caused by something that vpython does.

But it also occurred only once. The next build is green. May be some weird flake not worth digging into.

It looks like python failed to read some data which happened when zip_build.py used subprocess to call into gsutil. I think this is just a weird flake that isn't worth looking into. I'm not even sure how we could reproduce this... Closing for now, if it happens again we can look into it again.