Publishing machinery should not pass around traceback objects

[Chris McDonough]

From an email thread on Zope-dev:

>>>On a different subject, the publisher probably shouldn't pass around
>>>traceback objects (e.g. when it calls into err_hook) as Tres believes
>>>that may be a memory leak waiting to happen.
>>
>>The traceback is vital for error analysis.
>>
>>It may not be necessary that ZPublisher touches the traceback
>>but we will definitely need access to it during error handling.

Because the traceback contains stack frames, passing it through another
stack frame (via a function call) is inherently tricky: the called
function must *not* raise another exception.

> Perhaps the traceback can be passed as a string to avoid leaks?
> Furthermore why can't the traceback be retrieved later from
> sys.exc_info()?

+1; I don't want untrusted code handling tracebacks anyway.

[Tres Seaver (tseaver)]

This isn't a bug report: it is an invitation to a deep dive research project.

Please open a new issue with specifics if you disagree.