Bug#1028716: mozjs102: FTBFS with python3.11 as default: ValueError: invalid mode: 'rU'

[Simon McVittie]

Control: retitle -1 mozjs102: FTBFS with python3.11 as default: ValueError: invalid mode: 'rU'

On Sat, 14 Jan 2023 at 13:27:34 +0100, Lucas Nussbaum wrote:
> During a rebuild of all packages in sid, your package failed to build
> on amd64.
> 
> Relevant part (hopefully):
> > /usr/bin/ld: unrecognized option '--icf=safe'
> > /usr/bin/ld: use the --help option for usage information
> > collect2: error: ld returned 1 exit status

I don't think this is it: this is just an Autoconf feature-check for an
option that our compiler doesn't support. I think the actual error from
the log is this:

updating cache ./config.cache
creating ./config.data
Creating config.status
Traceback (most recent call last):
  File "/<<PKGBUILDDIR>>/js/src/../../configure.py", line 349, in <module>
    sys.exit(main(sys.argv))
             ^^^^^^^^^^^^^^
  File "/<<PKGBUILDDIR>>/js/src/../../configure.py", line 161, in main
    return config_status(config)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/<<PKGBUILDDIR>>/js/src/../../configure.py", line 281, in config_status
    partial_config.write_vars(sanitized_config)
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/backend/configenvironment.py", line 355, in write_vars
    self.substs._fill_group(substs)
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/backend/configenvironment.py", line 250, in _fill_group
    new_files.add(Path(self._write_file(k, v)))
                       ^^^^^^^^^^^^^^^^^^^^^^
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/backend/configenvironment.py", line 232, in _write_file
    with FileAvoidWrite(filename) as fh:
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/util.py", line 353, in __exit__
    self.close()
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/util.py", line 277, in close
    existing = _open(self.name, self.mode)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/<<PKGBUILDDIR>>/python/mozbuild/mozbuild/util.py", line 63, in _open
    return io.open(path, mode, encoding="utf-8", newline="\n")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: invalid mode: 'rU'
Configure failed with status 1

https://docs.python.org/3/whatsnew/3.11.html#porting-to-python-3-11 says:

> open(), io.open(), codecs.open() and fileinput.FileInput no longer
> accept 'U' (“universal newline”) in the file mode. In Python 3,
> “universal newline” mode is used by default whenever a file is opened
> in text mode, and the 'U' flag has been deprecated since Python 3.3. The
> newline parameter to these functions controls how universal newlines work.

    smcv