title: sqlalchemy ArgumentError: Textual SQL
body: <p>ArgumentError raises when passing plain text to "order_by".
  I'ts occurs with version 0.9.8, but not with version &lt; 0.9.8 or > 0.9.8.</p>
  
  <pre><code>q = session.query(Person)
  q.order_by('RAND()')
  &gt;&gt; ArgumentError: Textual SQL expression 'RAND()' should be explicitly declared as text('RAND()')
  </code></pre>
  
  <p>questions:
  1. Is there any official documentation about it?
  2. With new versions, is this a good practice to pass plain text, or it is better to wrap it with text()?
  3. Is this error raises with more functions other then order_by?</p>