The lzh_tw locale (Literary Chinese) is not available in Lib/locale.py

This issue will cause error like:

Traceback (most recent call last):
  File "/usr/share/apport/apport-gtk", line 598, in <module>
    app.run_argv()
  File "/usr/lib/python3/dist-packages/apport/ui.py", line 694, in run_argv
    return self.run_crashes()
  File "/usr/lib/python3/dist-packages/apport/ui.py", line 245, in run_crashes
    logind_session[1] > self.report.get_timestamp():
  File "/usr/lib/python3/dist-packages/apport/report.py", line 1684, in get_timestamp
    orig_ctime = locale.getlocale(locale.LC_TIME)
  File "/usr/lib/python3.6/locale.py", line 581, in getlocale
    return _parse_localename(localename)
  File "/usr/lib/python3.6/locale.py", line 490, in _parse_localename
    raise ValueError('unknown locale: %s' % localename)
ValueError: unknown locale: lzh_TW

This can be easily reproduced in Ubuntu 17.10, with English selected as the default language, but Timezone set to Taipei. This will set the locale to:

$ locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=lzh_TW
LC_TIME=lzh_TW
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=lzh_TW
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=lzh_TW
LC_NAME=lzh_TW
LC_ADDRESS=lzh_TW
LC_TELEPHONE=lzh_TW
LC_MEASUREMENT=lzh_TW
LC_IDENTIFICATION=lzh_TW
LC_ALL=

And when running some python script to call locale.py, you will see the error message above.