ImportError：为Django邀请运行迁移时，无法导入名称“ python_2_unicode_compatible”

首先，我想提一下我是Django的初学者。我正在尝试在我的应用程序上安装Django-Invitations以发送注册邀请。我按照他们的自述文件说明进行操作。

pip install django-invitations

# Add to settings.py, INSTALLED_APPS
'invitations',

# Append to urls.py
url(r'^invitations/', include('invitations.urls', namespace='invitations')),

# Run migrations
python manage.py migrate

我也从他们的需求文件中安装了所有需求：

覆盖率== 4.5.4 flake8 == 3.7.9 Frozengun == 0.3.12模拟== 3.0.5 pytest == 5.2.2 pytest-django == 3.6.0 pytest-cov == 2.8.1 tox == 3.14 .0

但是，当我第一次运行迁移时，我仍然遇到相同的错误：

Traceback (most recent call last):
  File "manage.py", line 21, in <module>
    main()
  File "manage.py", line 17, in main
    execute_from_command_line(sys.argv)
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\django\core\management\__init__.py", line 377, in execute
    django.setup()
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\django\apps\registry.py", line 114, in populate
    app_config.import_models()
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\django\apps\config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "C:\Users\maxim\AppData\Local\Programs\Python\Python36-32\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
  File "C:\Users\maxim\Desktop\Web Development\Projects\admin\RentQ3\myEnv\lib\site-packages\invitations\models.py", line 12, in <module>
    from django.utils.encoding import python_2_unicode_compatible
ImportError: cannot import name 'python_2_unicode_compatible'

知道可能是什么问题吗？

谢谢！