title: SAWarning: At least one scoped session is already present
body: <p>I have purposefully defined 2 different engines (using the same DB URL) meant for 2 sessions with different configuration, Pyramid's <code>model.py</code>:</p>
  
  <pre><code>DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
  
  DBSessionTask = scoped_session(sessionmaker(extension=ZopeTransactionExtension(), expire_on_commit=False))
  </code></pre>
  
  <p>Configuring sessions (in Pyramid app's main <code>__init__.py</code>):</p>
  
  <pre><code>engine = engine_from_config(settings, 'sqlalchemy.')
  DBSession.configure(bind=engine)
  Base.metadata.bind = engine
  
  engine_task = engine_from_config(settings, 'sqlalchemy.')
  DBSessionTask.configure(bind=engine_task)
  </code></pre>
  
  <p>The sessions are meant to be used for 2 different categories of objects (<code>DBSessionTask</code> for long-running supervision objects kept in the app-wide settings, <code>DBSession</code> for typical scoped session on "data" objects of a web app).</p>
  
  <p>I'm getting a warning:</p>
  
  <pre><code>sqlalchemy\orm\scoping.py:99: SAWarning: At least one scoped session is already present.  configure() can not affect sessions that have already been created.
    warn('At least one scoped session is already present. '
  </code></pre>
  
  <p>Those are 2 different engines, so why SQA is warning me about it? They're using the same DB url of course, but why should that be a problem?</p>