title: Cannot overwrite default django database settings
body: <p>I've got a problem with Django DATABASES setting in settings.py.
  I'm using Python 3.4.3, Django 1.10.5 and psycopg 2.6.1</p>
  
  <p>if my code looks like</p>
  
  <pre><code>        DATABASES = { 
              'default':{
                    'ENGINE': 'django.db.backends.postgresql_psycopg2', 
                          'NAME': ' dbname',
                          'USER': 'postgres',
                          'PASSWORD': 'dbpass',
                          'HOST': 'localhost',
                          'PORT': '5432',
      }
  }
  </code></pre>
  
  <p>and i run manage.py diffsettings  in DATABASE section there are some default settings:</p>
  
  <pre><code>DATABASES = {'default': {'USER': '', 'HOST': '', 'AUTOCOMMIT': True, 'NAME': '', 'ATOMIC_REQUESTS': False, 'OPTIONS': {}, 'TEST': {'MIRROR': None, 'CHARSET': None, 'NAME': None, 'COLLATION': None}, 'ENGINE': 'django.db.backends.dummy', 'PASSWORD': '', 'CONN_MAX_AGE': 0, 'TIME_ZONE': None, 'PORT': ''}}
  </code></pre>
  
  <p>but when I change 'default' to 'db' (or any other name)</p>
  
  <pre><code>       DATABASES = { 
              'db':{
                    'ENGINE': 'django.db.backends.postgresql_psycopg2', 
                          'NAME': ' dbname',
                          'USER': 'postgres',
                          'PASSWORD': 'dbpass',
                          'HOST': 'localhost',
                          'PORT': '5432',
      }
  }
  </code></pre>
  
  <p>the manage.py diffsettings 'knows'  the database db:</p>
  
  <pre><code>DATABASES = {'db': {'NAME': 'dbname', 'HOST': 'localhost', 'PORT': '5432', 'PASSWORD': 'dbpass', 'ENGINE': 'django.db.backends.postgresql_psycopg2', 'USER': 'postgres'}, 'default': {'OPTIONS': {}, 'ATOMIC_REQUESTS': False, 'HOST': '', 'AUTOCOMMIT': True, 'PASSWORD': '', 'USER': '', 'TIME_ZONE': None, 'NAME': '', 'PORT': '', 'CONN_MAX_AGE': 0, 'ENGINE': 'django.db.backends.dummy', 'TEST': {'NAME': None, 'MIRROR': None, 'COLLATION': None, 'CHARSET': None}}}
  </code></pre>
  
  <p>What should I to to use my database as a default and don't have to use DATABASE_ROUTERS ?</p>