See https://github.com/python/asyncio/pull/295 for details

not to IDLE itself.

Don't fallback to PyDict_GetItemWithError() if the hash is unknown: compute the
hash instead. Add also comments to explain the optimization a little bit.

Issue #25472: In B[<type>], insert B in front of __bases__, to make the __dict__ descriptor work. (Merge 3.5->3.6)