test_gdb failed on a lot of buildbots. Examples:

* http://buildbot.python.org/all/builders/PPC64%20Fedora%203.x/builds/2089
* http://buildbot.python.org/all/builders/AMD64%20Debian%20PGO%203.6/builds/330
* http://buildbot.python.org/all/builders/x86%20Gentoo%20Non-Debug%20with%20X%203.6/builds/287

Extract of the Gentoo non-debug:

(...)
    GNU gdb (Gentoo 7.10.1 vanilla) 7.10.1
(...)
======================================================================
FAIL: test_NULL_ob_type (test.test_gdb.PrettyPrintTests)
Ensure that a PyObject* with NULL ob_type is handled gracefully
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 490, in test_NULL_ob_type
    'set v->ob_type=0')
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 461, in assertSane
    cmds_after_breakpoint=cmds_after_breakpoint)
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 240, in get_gdb_repr
    import_site=import_site)
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 218, in get_stack_trace
    self.assertEqual(unexpected_errlines, [])
AssertionError: Lists differ: ["Python Exception <class 'gdb.error'> Can[663 chars].: "] != []

First list contains 10 additional elements.
First extra element 0:
"Python Exception <class 'gdb.error'> Cannot convert value to int.: "

Diff is 745 characters long. Set self.maxDiff to None to see it.