Access the key that was looked up in a way that will result in the

same output for both Python 2.2 and 2.3.

Python 2.3 changes the str() of KeyError exceptions to return a repr()
of the key instead of the str() of the key, which caused quotes to be
generated if we don't pick out just the key.

lib/python/Products/PageTemplates/tests/input/CheckPathAlt.html

@@ -15,7 +15,7 @@
    <p tal:attributes="name y/z | python:'||'[:0]">Z</p>
    <p tal:attributes="name y/z | nothing">Z</p>
 
-   <p tal:on-error="python:str(error.value)" tal:content="a/b | c/d">Z</p>
+   <p tal:on-error="python:str(error.value[0])" tal:content="a/b | c/d">Z</p>
    </div>
 </body>
 </html>