我的Django项目现在不能运行Python3 manage.py runserver了。

因此，我在堆栈这里看到了这个问题，但有几个稍微不同的原因，我无法自己设法弄清楚它。

我在我的终端中得到这个错误。

Traceback (most recent call last):
  File "manage.py", line 10, in main
    from django.core.management import execute_from_command_line
ModuleNotFoundError: No module named 'django'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "manage.py", line 21, in <module>
    main()
  File "manage.py", line 12, in main
    raise ImportError(
ImportError: Couldn't import Django. Are you sure it's installed and available on your PYTHONPATH environment variable? Did you forget to activate a virtual environment?
是的，我确实安装了django。
我目前正在做哈佛CS50W项目，在我通过HomeBrew更新我的python之前，它一直工作得非常好。