WPT export broken under Python 3

[Sam Sneddon [:gsnedders]]

Via Antti:

> I’m getting:

Fetching: https://bugs.webkit.org/show_bug.cgi?id=238542&ctype=xml&excludefield=attachmentdata
Removing local branch wpt-export-for-webkit-238542
Finished
Cleaning web-platform-tests master branch
Traceback (most recent call last):
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/test_exporter.py", line 350, in create_wpt_pull_request
    pr_number = self._github.create_pr(remote_branch_name, title, body)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/wpt_github.py", line 152, in create_pr
    response = self.request(path, method='POST', body=body)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/wpt_github.py", line 95, in request
    response = self.host.web.request(
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/common/net/web.py", line 51, in request
    return opener.open(request)
  File ".../Python.framework/Versions/3.8/lib/python3.8/urllib/request.py", line 522, in open
    req = meth(req)
  File ".../Python.framework/Versions/3.8/lib/python3.8/urllib/request.py", line 1285, in do_request_
    raise TypeError(msg)
TypeError: POST data should be bytes, an iterable of bytes, or a file object. It cannot be of type str.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/antti/webkit/OpenSource/Tools/Scripts//webkit-patch", line 80, in <module>
    main()
  File "/Users/antti/webkit/OpenSource/Tools/Scripts//webkit-patch", line 75, in main
    WebKitPatch(os.path.abspath(__file__)).main()
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/multicommandtool.py", line 305, in main
    result = command.check_arguments_and_execute(options, args, self)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/multicommandtool.py", line 123, in check_arguments_and_execute
    return self.execute(options, args, tool) or 0
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/commands/abstractsequencedcommand.py", line 55, in execute
    self._sequence.run_and_handle_errors(tool, options, state)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/commands/stepsequence.py", line 73, in run_and_handle_errors
    self._run(tool, options, state)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/commands/stepsequence.py", line 67, in _run
    step(tool, options).run(state)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/tool/steps/wptchangeexport.py", line 53, in run
    test_exporter.do_export()
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/test_exporter.py", line 397, in do_export
    self.make_pull_request()
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/test_exporter.py", line 336, in make_pull_request
    pr_number = self.create_wpt_pull_request(self._wpt_fork_remote + ':' + self._public_branch_name, self._commit_message, description)
  File "/Users/antti/webkit/OpenSource/Tools/Scripts/webkitpy/w3c/test_exporter.py", line 352, in create_wpt_pull_request
    if e.code == 422:
AttributeError: 'TypeError' object has no attribute 'code'

[Sam Sneddon [:gsnedders]]

Created attachment 456567 [details]
Patch

[EWS]

Committed r292288 (249186@main): <https://commits.webkit.org/249186@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 456567 [details].

[Radar WebKit Bug Importer]

<rdar://problem/91241469>