Merge pull request #9389 from y-zeng/registry_comments

Document new args in grpc_resolver_create
diff --git a/tools/dockerfile/interoptest/grpc_interop_http2/Dockerfile b/tools/dockerfile/interoptest/grpc_interop_http2/Dockerfile
index 05e963d..03ff179 100644
--- a/tools/dockerfile/interoptest/grpc_interop_http2/Dockerfile
+++ b/tools/dockerfile/interoptest/grpc_interop_http2/Dockerfile
@@ -46,6 +46,7 @@
 RUN pip install pip --upgrade
 RUN pip install virtualenv
 RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.0.0a2 six==1.10.0
+RUN pip install twisted h2
 
 # Define the default command.
 CMD ["bash"]