Merge pull request #2088 from tseaver/1863-appveyou-pin-grpcio-1.0rc1

Appveyor:  force install grpcio >= 1.0rc1.

Author: tseaver

appveyor.yml

@@ -82,9 +82,9 @@ install:
   # compiled extensions and are not provided as pre-built wheel packages,
   # pip will build them from source using the MSVC compiler matching the
   # target Python version and architecture
-  - "%CMD_IN_ENV% pip install wheel nose nose-exclude cryptography grpcio"
-  # Install sometimes-problemaatic gRPC-related dependencies
-  - "%CMD_IN_ENV% pip install grpcio gax-google-pubsub-v1 gax-google-logging-v2"
+  - "%CMD_IN_ENV% pip install wheel nose nose-exclude cryptography"
+  # Install sometimes-problematic gRPC-related dependencies
+  - "%CMD_IN_ENV% pip install 'grpcio >= 1.0rc1' gax-google-pubsub-v1 gax-google-logging-v2"
 
 build_script:
   # Build the compiled extension