Just got this error when uploading a new patch to a CL in the infra repo:

$ git cl upload
...
remote: Updated Changes:        
remote:   https://chromium-review.googlesource.com/388612 w3c-test-autoroller: Checkout new branch for updating csswg-test.        
remote: 
To https://chromium.googlesource.com/infra/infra.git
 * [new branch]      d77a1b34c2755a55769e4d7513f20c7c51a47851 -> refs/for/refs/heads/master%notify=NONE
Traceback (most recent call last):
  File ".../depot_tools/git_cl.py", line 5305, in <module>
    sys.exit(main(sys.argv[1:]))
  File ".../depot_tools/git_cl.py", line 5287, in main
    return dispatcher.execute(OptionParser(), argv)
  File ".../depot_tools/subcommand.py", line 252, in execute
    return command(parser, args[1:])
  File ".../depot_tools/git_cl.py", line 3984, in CMDupload
    return cl.CMDUpload(options, args, orig_args)
  File ".../depot_tools/git_cl.py", line 1493, in CMDUpload
    ret = self.CMDUploadChange(options, git_diff_args, change)
  File ".../depot_tools/git_cl.py", line 2666, in CMDUploadChange
    self._GetGerritHost(), self.GetIssue(), cc, is_reviewer=False)
  File ".../depot_tools/gerrit_util.py", line 629, in AddReviewers
    jmsg = ReadHttpJsonResponse(conn, ignore_404=False)
  File ".../depot_tools/gerrit_util.py", line 356, in ReadHttpJsonResponse
    conn, expect_status=expect_status, ignore_404=ignore_404)
  File ".../depot_tools/gerrit_util.py", line 349, in ReadHttpResponse
    raise GerritError(response.status, reason)
gerrit_util.GerritError: Unprocessable Entity:  infra-reviews+infra@chromium.org does not identify a registered user or group

Note: The patch was successfully uploaded before it hit the error.