text: Title: environ error
  Body: After going through the setup, I try to get it running by starting `./manage.py runserver` - but it crashes:
  ```
  Traceback (most recent call last):
    File "./manage.py", line 27, in <module>
      execute_from_command_line(sys.argv)
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/django/core/management/__init__.py", line 325, in execute
      settings.INSTALLED_APPS
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/django/conf/__init__.py", line 79, in __getattr__
      self._setup(name)
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/django/conf/__init__.py", line 66, in _setup
      self._wrapped = Settings(settings_module)
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/django/conf/__init__.py", line 157, in __init__
      mod = importlib.import_module(self.SETTINGS_MODULE)
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/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/christian/tmp/cookiecutter-django-vue/medux/backend/config/settings.py", line 10, in <module>
      import environ
    File "/home/christian/.local/share/virtualenvs/cookiecutter-django-vue-L7tyPivc/lib/python3.7/site-packages/environ.py", line 114
      raise ValueError, "No frame marked with %s." % fname
                      ^
  SyntaxError: invalid syntax
  ```
  
  This mainly isn't your fault mainly, because it seems that the environ module you are importing has a problem using the old Python2 syntax - which seems not working here...
  
  Do you officially support Python3? The "environ" module was released in 2007 on pypi, which is - kind of - outdated ;-)
  
  Could you please move to something else - e.g. `os.environ`?