Tracebacks with gevent and set_wait_callback go "missing"

Hi all,

I'm trying to debug an issue I'm seeing in production, whereby
traceback information about an exception is missing. This is
incredibly frustrating as it makes it extremely difficult to track
down errors. This has been observed before, as I found a ticket on the
Gunicorn GitHub site relating to this:

https://github.com/benoitc/gunicorn/issues/214

Specifically, what happens is when an exception is raised, the
traceback part of sys.exc_info() is None. To me, it seems the most
likely suspect is psycopg2, since this is going into C-land (though
obviously not the only possible explanation). I was wondering if
anyone on this else knows of this issue, or anything that may cause
it?

Many thanks!

– Oliver