title: django.db.utils.OperationalError: unable to open database file
body: <p>When I run</p>
  
  <pre><code>python manage.py runserver
  </code></pre>
  
  <p>I get this error</p>
  
  <p>File "/usr/local/lib/python2.7/dist-packages/Django-1.10.1-py2.7.egg/django/db/backends/sqlite3/base.py", line 209, in get_new_connection
      conn = Database.connect(**conn_params)
  django.db.utils.OperationalError: unable to open database file</p>
  
  <p>my settings.py:</p>
  
  <pre><code>DATABASES = {
      'default': dj_database_url.config(
          default="sqlite:///{}".format(
              os.path.join(BASE_DIR, 'db/db.sqlite3')
          )
      )
  }
  </code></pre>