Revert "Upgrade python/mock to 4.0.2" am: 3381fde741 am: 276f8d6022 am: 4837d7c35e am: 9d5d8fdcb7 am: 4538b16524

Change-Id: Ifcfb18de8d3a058270f0f9b8517735ab0bf6d71e