title: Python unittest - opposite of assertRaises?
body: <p>I want to write a test to establish that an Exception is not raised in a given circumstance. </p>
  
  <p>It's straightforward to test if an Exception <strong>is</strong> raised ...</p>
  
  <pre><code>sInvalidPath=AlwaysSuppliesAnInvalidPath()
  self.assertRaises(PathIsNotAValidOne, MyObject, sInvalidPath) 
  </code></pre>
  
  <p>... but how can you do the <strong>opposite</strong>. </p>
  
  <p>Something like this i what I'm after ...</p>
  
  <pre><code>sValidPath=AlwaysSuppliesAValidPath()
  self.assertNotRaises(PathIsNotAValidOne, MyObject, sValidPath) 
  </code></pre>