Raised KeyError exception is being quoted twice
<p>So I have a to string method in one of my classes:</p>

<pre><code>def __str__(self):
    # some irrelevant code
    raise KeyError("aaa")
</code></pre>

<p>Then in my tests I do:</p>

<pre><code>with self.assertRaises(KeyError) as cm:
    str(myobject)
self.assertEquals("%s" % cm.exception, "aaa")
</code></pre>

<p>I get this output:</p>

<pre><code>self.assertEquals("%s" % cm.exception, "aaa")
AssertionError: "'aaa'" != 'aaa'
</code></pre>

<p>Any ideas what could be causing this?</p>
