Fix Python server interop spec noncompliance

Also fix spelling mistakes in the spec itself.

doc/interop-test-descriptions.md

@@ -968,8 +968,8 @@ request payload bodies received.
 [StreamingOutputCall]: #streamingoutputcall
 
 Server implements StreamingOutputCall by replying, in order, with one
-StreamingOutputCallResponses for each ResponseParameters in
-StreamingOutputCallRequest. Each StreamingOutputCallResponses should have a
+StreamingOutputCallResponse for each ResponseParameters in
+StreamingOutputCallRequest. Each StreamingOutputCallResponse should have a
 payload body of size ResponseParameters.size bytes, as specified by its
 respective ResponseParameters. After sending all responses, it closes with OK.
 
@@ -977,8 +977,8 @@ respective ResponseParameters. After sending all responses, it closes with OK.
 [FullDuplexCall]: #fullduplexcall
 
 Server implements FullDuplexCall by replying, in order, with one
-StreamingOutputCallResponses for each ResponseParameters in each
-StreamingOutputCallRequest. Each StreamingOutputCallResponses should have a
+StreamingOutputCallResponse for each ResponseParameters in each
+StreamingOutputCallRequest. Each StreamingOutputCallResponse should have a
 payload body of size ResponseParameters.size bytes, as specified by its
 respective ResponseParameters. After receiving half close and sending all
 responses, it closes with OK.

src/python/grpcio/tests/interop/methods.py

@@ -79,10 +79,11 @@ class TestService(test_pb2.BetaTestServiceServicer):
 
   def FullDuplexCall(self, request_iterator, context):
     for request in request_iterator:
-      yield messages_pb2.StreamingOutputCallResponse(
-          payload=messages_pb2.Payload(
-              type=request.payload.type,
-              body=b'\x00' * request.response_parameters[0].size))
+      for response_parameters in request.response_parameters:
+        yield messages_pb2.StreamingOutputCallResponse(
+            payload=messages_pb2.Payload(
+                type=request.payload.type,
+                body=b'\x00' * response_parameters.size))
 
   # NOTE(nathaniel): Apparently this is the same as the full-duplex call?
   # NOTE(atash): It isn't even called in the interop spec (Oct 22 2015)...