title: Django manage.py migrate error
body: <p>So I am currently in a virtual environment, and when I typed the command line: </p>
  
  <pre><code>python manage.py migrate
  </code></pre>
  
  <p>and I encounter this problem: </p>
  
  <pre><code>&gt;     Traceback (most recent call last):
  &gt;       File "manage.py", line 24, in &lt;module&gt;
  &gt;         execute_from_command_line(sys.argv)
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\core\management\__init__.py",
  &gt; line 371, in execute_from_command_line
  &gt;         utility.execute()
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\core\management\__init__.py",
  &gt; line 317, in execute
  &gt;         settings.INSTALLED_APPS
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
  &gt; line 56, in __getattr__
  &gt;         self._setup(name)
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
  &gt; line 43, in _setup
  &gt;         self._wrapped = Settings(settings_module)
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\site-packages\django\conf\__init__.py",
  &gt; line 106, in __init__
  &gt;         mod = importlib.import_module(self.SETTINGS_MODULE)
  &gt;       File "C:\Users\DUCNGU~1\Desktop\HAULER~1\api\vnenv\lib\importlib\__init__.py",
  &gt; line 126, in import_module
  &gt;         return _bootstrap._gcd_import(name[level:], package, level)
  &gt;       File "&lt;frozen importlib._bootstrap&gt;", line 994, in _gcd_import
  &gt;       File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
  &gt;       File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
  &gt;       File "&lt;frozen importlib._bootstrap&gt;", line 665, in _load_unlocked
  &gt;       File "&lt;frozen importlib._bootstrap_external&gt;", line 678, in exec_module
  &gt;       File "&lt;frozen importlib._bootstrap&gt;", line 219, in _call_with_frames_removed
  &gt;       File "C:\Users\Duc Nguyen\Desktop\HaulerAds\api\settings.py", line 104, in &lt;module&gt;
  &gt;         'PORT': int(os.getenv('POSTGRES_PORT')),
  &gt;     TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
  </code></pre>
  
  <p>My current Django version 2.0.3. I checked the python pass and I have the proper path. 
  Please help, thank you!</p>