Merge pull request #10038 from mehrdada/server-reflection-for-grpc-python

Bump protobuf to 3.2.0 in requirements.txt

requirements.txt

@@ -3,6 +3,6 @@ coverage>=4.0
 cython>=0.23
 enum34>=1.0.4
 futures>=2.2.0
-protobuf>=3.0.0
+protobuf>=3.2.0
 six>=1.10
 wheel>=0.29