Update: when I try to git cl upload an update to this patch, it won't let me, similar stack trace:

Traceback (most recent call last):
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 5403, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 5385, in main
    return dispatcher.execute(OptionParser(), argv)
  File "/usr/local/google/home/npm/depot_tools/subcommand.py", line 252, in execute
    return command(parser, args[1:])
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 4210, in CMDupload
    return cl.CMDUpload(options, args, orig_args)
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 1575, in CMDUpload
    change = self.GetChange(base_branch, None)
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 1504, in GetChange
    description = self.GetDescription()
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 1426, in GetDescription
    self.description = self._codereview_impl.FetchDescription()
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 2462, in FetchDescription
    data = self._GetChangeDetail(['CURRENT_REVISION'])
  File "/usr/local/google/home/npm/depot_tools/git_cl.py", line 2504, in _GetChangeDetail
    raise GerritIssueNotExists(issue, self.GetCodereviewServer())
__main__.GerritIssueNotExists:  issue 2031  at https://pdfium-review.googlesource.com does not exist or you have no access to it

ping

The likely explanation is this:

* pdfium-review allows Push on refs/for/* to Registered Users. So you can create a CL, whether or not you're recognized as a specially-ACL'd contributor.
* but, you're not being recognized as a member of pdfium-committers, so it's not letting you do other things (like set reviewers, or upload additional patchsets).

That means that you probably have a credential failure. What email address is set as "git config user.email" in this repo? Is that email address also used on the "pdfium-review.googlesource.com" line of your .gitcookies file?

The email given by "git config user.email" is npm@chromium.org, and I checked that the line for pdfium-review.googlesource.com in gitcookies includes "git-npm.chromium.org=1". Also,
git cl upload (uploading to https://codereview.chromium.org in pdfium) works fine for me. Are the permissions different?

Yeah, the permissions for codereview.chromium.org and pdfium-review.googlesource.com are so different they're not even comparable.

Hmm, you're definitely in pdfium-committers: https://pdfium-review.googlesource.com/#/admin/groups/uuid-483267b793affc296ed656cfbf210ca92d04d566
And pdfium-committers can definitely add patch sets to any review: https://pdfium-review.googlesource.com/#/admin/projects/All-Projects,access

Is there another line in your .gitcookies for just "googlesource.com", with no subdomain? If so, it is probably overriding the one for pdfium-review.

Oh, yes there is. It's below the other one (I don't know if order matters), and has my @google email.

I'm also not sure if it uses order (last overrides others) or something else (most general wins) but I've seen this cause problems before. The best solution is to remove the generic googlesource.com line, and only have lines for each individual foo.googlesource.com host you actually use.

Changing the order did not work. So I just got rid of the googlesource.com line. Thanks.