Crypt Docker fails to run if LANG is not set to en

[natewalck]

Currently, the Docker container is failing with the following error:

SystemCheckError: System check identified some issues:
ERRORS:
?: (translation.E001) You have provided an invalid value for the LANGUAGE_CODE setting.

If you use LANG=en it works fine.

If you set it to en-US, it doesn't recognize it (as en-us appears to be what django is klooking for).
Full trace:

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.7/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.7/site-packages/django/core/management/base.py", line 361, in execute
    self.check()
  File "/usr/local/lib/python3.7/site-packages/django/core/management/base.py", line 390, in check
    include_deployment_checks=include_deployment_checks,
  File "/usr/local/lib/python3.7/site-packages/django/core/management/commands/migrate.py", line 65, in _run_checks
    issues.extend(super()._run_checks(**kwargs))
  File "/usr/local/lib/python3.7/site-packages/django/core/management/base.py", line 377, in _run_checks
    return checks.run_checks(**kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/core/checks/registry.py", line 72, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/usr/local/lib/python3.7/site-packages/django/core/checks/urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File "/usr/local/lib/python3.7/site-packages/django/core/checks/urls.py", line 23, in check_resolver
    return check_method()
  File "/usr/local/lib/python3.7/site-packages/django/urls/resolvers.py", line 399, in check
    for pattern in self.url_patterns:
  File "/usr/local/lib/python3.7/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/usr/local/lib/python3.7/site-packages/django/urls/resolvers.py", line 584, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "/usr/local/lib/python3.7/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/usr/local/lib/python3.7/site-packages/django/urls/resolvers.py", line 577, in urlconf_module
    return import_module(self.urlconf_name)
  File "/usr/local/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/docker/crypt/fvserver/urls.py", line 3, in <module>
    from .origurls import *
  File "/home/docker/crypt/fvserver/origurls.py", line 8, in <module>
    import django.contrib.admindocs.urls as admindocs_urls
  File "/usr/local/lib/python3.7/site-packages/django/contrib/admindocs/urls.py", line 1, in <module>
    from django.contrib.admindocs import views
  File "/usr/local/lib/python3.7/site-packages/django/contrib/admindocs/views.py", line 9, in <module>
    from django.contrib.admindocs import utils
  File "/usr/local/lib/python3.7/site-packages/django/contrib/admindocs/utils.py", line 11, in <module>
    import docutils.core
  File "/usr/local/lib/python3.7/site-packages/docutils/core.py", line 20, in <module>
    from docutils import frontend, io, utils, readers, writers
  File "/usr/local/lib/python3.7/site-packages/docutils/frontend.py", line 41, in <module>
    import docutils.utils
  File "/usr/local/lib/python3.7/site-packages/docutils/utils/__init__.py", line 20, in <module>
    import docutils.io
  File "/usr/local/lib/python3.7/site-packages/docutils/io.py", line 18, in <module>
    from docutils.utils.error_reporting import locale_encoding, ErrorString, ErrorOutput
  File "/usr/local/lib/python3.7/site-packages/docutils/utils/error_reporting.py", line 47, in <module>
    locale_encoding = locale.getlocale()[1] or locale.getdefaultlocale()[1]
  File "/usr/local/lib/python3.7/locale.py", line 587, in getlocale
    return _parse_localename(localename)
  File "/usr/local/lib/python3.7/locale.py", line 495, in _parse_localename
    raise ValueError('unknown locale: %s' % localename)
ValueError: unknown locale: en-US

[grahamgilbert]

Sounds like a simple PR to this line, no? https://github.com/grahamgilbert/Crypt-Server/blob/master/Dockerfile#L7