Merged requested to merge bitbucket/merged-pr-626 into branch/py3.6
Created originally on Bitbucket by davidcellis (David Ellis)
Was already merged in Bitbucket before import, marked as merged by the import user
Add GC collect to lock_tests weakref delete test.
Add GC collects to test_warnings test_tracemalloc
- Gives the expected warning class
- Test still fails as the message is different to CPython