title: Pyramid fails to start when webtest and sqlalchemy are used together
body: <p>I am trying to setup a pyramid app to use both webtest and sqlalchemy.
  If I comment out the SQLAlchemy code, the webtests run without a problem.</p>
  
  <p>[Test log ] <a href="https://travis-ci.org/caffeinated-expert/frisbee/builds/91622436" rel="nofollow">https://travis-ci.org/caffeinated-expert/frisbee/builds/91622436</a></p>
  
  <pre><code>Error
  Traceback (most recent call last):
    File "frisbee/frisbee/tests/test_cities_page.py", line 18, in setUp
      app = main({})
    File "frisbee/frisbee/__init__.py", line 15, in main
      engine = engine_from_config(settings, 'sqlalchemy.')
    File "build/bdist.macosx-10.10-x86_64/egg/sqlalchemy/engine/__init__.py", line 426, in engine_from_config
      url = options.pop('url')
  KeyError: 'url'
  </code></pre>
  
  <p>In my main <strong>init</strong> file, if I comment out the sqlalchemy engine setup, then the tests run fine, but I need sqlalchemy for my project.</p>
  
  <p>This is is the first time I have used webtest, so not sure if I have some other conflicting config.</p>
  
  <p>[Failing code] <a href="https://github.com/caffeinated-expert/frisbee/commit/ea759015de755aca1d7bffca2845b72944572bed" rel="nofollow">https://github.com/caffeinated-expert/frisbee/commit/ea759015de755aca1d7bffca2845b72944572bed</a></p>