Ubuntu更新后环境混乱

Question

我已经将Ubuntu更新到20.04。更新之后，当我运行python manage.py runserver时，我得到了：

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'

我看到pyhon 3.8随更新一起安装，所以我尝试运行python3.6 manage.py runserver并得到：

django.core.management.base.SystemCheckError: SystemCheckError: System check identified some issues:

ERRORS:
mtn.Image.image: (fields.E210) Cannot use ImageField because Pillow is not installed.
    HINT: Get Pillow at https://pypi.org/project/Pillow/ or run command "python -m pip install Pillow".

我尝试了pip3 install Pillow和pip3.6 install Pillow并得到了ModuleNotFoundError: No module named 'pip._vendor.packaging.tags'。 其他人在更新后有此问题吗？