Fix doctest example with exception

Python traceback contains details that are likely to change depending
on the execution environment, these details can be ignored.
While the correct exception type (AssertionError) remains unchanged.

eventlet/event.py

@@ -152,9 +152,8 @@ def send(self, result=None, exc=None):
 
         It is an error to call :meth:`send` multiple times on the same event.
 
-        >>> evt.send('whoops')
+        >>> evt.send('whoops') # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
-        ...
         AssertionError: Trying to re-send() an already-triggered event.
 
         Use :meth:`reset` between :meth:`send` s to reuse an event object.