https://chromium-review.googlesource.com/c/chromium/src/+/1018012 moves a subdir around and updates OWNERS files. Specifically:

src/chrome_cleaner/OWNERS -> src/chrome/chrome_cleaner/OWNERS

file:// references in components/chrome_cleaner/OWNERS and chrome/browser/safe_browsing/chrome_cleaner/OWNERS are updated to point to the new location:

file://chrome_cleaner/OWNERS -> file://chrome/chrome_cleaner/OWNERS

The presubmit hooks for this CL fail with:

Traceback (most recent call last):
  File "C:\src\depot_tools\git_cl.py", line 6038, in <module>
    sys.exit(main(sys.argv[1:]))
  File "C:\src\depot_tools\git_cl.py", line 6020, in main
    return dispatcher.execute(OptionParser(), argv)
  File "C:\src\depot_tools\subcommand.py", line 252, in execute
    return command(parser, args[1:])
  File "C:\src\depot_tools\git_cl.py", line 5058, in CMDupload
    return cl.CMDUpload(options, args, orig_args)
  File "C:\src\depot_tools\git_cl.py", line 1595, in CMDUpload
    change=change, parallel=options.parallel)
  File "C:\src\depot_tools\git_cl.py", line 1529, in RunHook
    parallel=parallel)
  File "C:\src\depot_tools\presubmit_support.py", line 1558, in DoPresubmitChecks
    results += executer.ExecPresubmitScript(presubmit_script, filename)
  File "C:\src\depot_tools\presubmit_support.py", line 1465, in ExecPresubmitScript
    result = eval(function_name + '(*__args)', context)
  File "<string>", line 1, in <module>
  File "<string>", line 3199, in CheckChangeOnUpload
  File "<string>", line 2766, in _CommonChecks
  File "C:\src\depot_tools\presubmit_canned_checks.py", line 1003, in PanProjectChecks
    input_api, output_api, source_file_filter=None))
  File "C:\src\depot_tools\presubmit_canned_checks.py", line 865, in CheckOwners
    override_files=input_api.change.OriginalOwnersFiles())
  File "C:\src\depot_tools\owners_finder.py", line 40, in __init__
    self.db.load_data_needed_for(files)
  File "C:\src\depot_tools\owners.py", line 216, in load_data_needed_for
    self._read_owners(self.os_path.join(dirpath, 'OWNERS'))
  File "C:\src\depot_tools\owners.py", line 305, in _read_owners
    ' '.join(comment))
  File "C:\src\depot_tools\owners.py", line 357, in _add_entry
    ('%s does not refer to an existing file.' % directive[5:]))
owners.SyntaxErrorInOwnersFile: C:\src\chromium\src\components\chrome_cleaner\OWNERS:1 syntax error: //chrome_cleaner/OWNERS does not refer
to an existing file.

It looks like it's trying to validate the before version of the file:// reference and not the after version.