Django manage.py迁移错误

所以我目前在虚拟环境中，当我输入命令行时：

python manage.py migrate

我遇到了这个问题：

>     Traceback (most recent call last):
>       File "manage.py", line 24, in <module>
>         execute_from_command_line(sys.argv)
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\core\management\__init__.py",
> line 371, in execute_from_command_line
>         utility.execute()
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\core\management\__init__.py",
> line 317, in execute
>         settings.INSTALLED_APPS
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
> line 56, in __getattr__
>         self._setup(name)
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
> line 43, in _setup
>         self._wrapped = Settings(settings_module)
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
> line 106, in __init__
>         mod = importlib.import_module(self.SETTINGS_MODULE)
>       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\importlib\__init__.py",
> line 126, in import_module
>         return _bootstrap._gcd_import(name[level:], package, level)
>       File "<frozen importlib._bootstrap>", line 994, in _gcd_import
>       File "<frozen importlib._bootstrap>", line 971, in _find_and_load
>       File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
>       File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
>       File "<frozen importlib._bootstrap_external>", line 678, in exec_module
>       File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
>       File "C:\Users\Duc Nguyen\Desktop\HaulerAds\api\settings.py", line 104, in <module>
>         'PORT': int(os.getenv('POSTGRES_PORT')),
>     TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'

我当前的Django版本2.0.3。我检查了python pass，并找到了正确的路径。请帮忙，谢谢！