Upgrade Python proto dependency to 3.0.0-alpha-1.
diff --git a/tools/run_tests/build_python.sh b/tools/run_tests/build_python.sh
index 3f39e56..3625412 100755
--- a/tools/run_tests/build_python.sh
+++ b/tools/run_tests/build_python.sh
@@ -11,5 +11,5 @@
 virtualenv python2.7_virtual_environment
 ln -sf $root/include/grpc python2.7_virtual_environment/include/grpc
 source python2.7_virtual_environment/bin/activate
-pip install enum34==1.0.4 futures==2.2.0 protobuf==2.6.1
+pip install enum34==1.0.4 futures==2.2.0 protobuf==3.0.0-alpha-1
 CFLAGS=-I$root/include LDFLAGS=-L$root/libs/opt pip install src/python/src