trigger it (other errors are not caught).  TALESError() takes up to
  three args: msg, position, info, where msg is the message string,
  position is a (lineno, offset) tuple, and info is the exception info
  tuple (type, value, traceback) from sys.exc_info().  Both default to
  tuples with all None values.  You can choose to subclass this
  exception of course.

- Require explicit </endtag> for <starttags> that have TAL or METAL
  attributes.  (Note that this detected a bug in the first example on
  http://dev.zope.org/Wikis/DevSite/Projects/ZPT/RenderErrorHandlingStrategies;
  the <span> wasn't closed.