This test case:

---
#!/usr/bin/env python

import gobject
import time

def do_idle():
    print "foo %d" % time.time ()
    return True
gobject.timeout_add (500, do_idle)

main_loop = gobject.MainLoop ()

time.sleep (1)
while main_loop.get_context ().pending ():
    main_loop.get_context ().iteration (False)
    time.sleep (1)
---

crashes from what looks to be this:

---
Fri Jul  1 18:51:15 PDT 2005  Manish Singh  <yosh@gimp.org>

        * gobject/pygmaincontext.c: unref the underlying GMainContext upon
        object destruction. Some minor cleanups as well.
---

Problem is that pyg_main_context_new() is the only place where we actually take
a ref on the GMainContext(). Two other places don't take a ref. Attaching a patch.