Revert "ci: Travis: remove pypy3 job for now"
Revert "ci: Travis: remove pypy3 job for now"

This reverts commit 47022b36cb5e235d26c1d50503c0705faf56e378.

markshao/pytest,nicoddemus/pytest,nicoddemus/pytest,The-Compiler/pytest,pytest-dev/pytest,Akasurde/pytest,tomviner/pytest,The-Compiler/pytest,tomviner/pytest,RonnyPfannschmidt/pytest,alfredodeza/pytest