Remove 2to3 code from setup.py. (#5114)
Remove 2to3 code from setup.py. (#5114)

Python protobuf has long been a single-source codebase. 2to3 shouldn't need to run in setup.py.
google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf