Send data to ServiceClients only if present (#39)

* Provide json data to service client only if present. Fixes #38 
* Scope requests to install internal dependencies for doc building. Fixes failing doc builds.

Author: nikhilym

ask-sdk-core/ask_sdk_core/api_client.py

@@ -66,7 +66,11 @@ def invoke(self, request):
                 raise ApiClientException(
                     "Requests against non-HTTPS endpoints are not allowed.")
 
-            raw_data = json.dumps(request.body)
+            if request.body:
+                raw_data = json.dumps(request.body)
+            else:
+                raw_data = None
+
             http_response = http_method(
                 url=request.url, headers=http_headers, data=raw_data)
 

ask-sdk-core/requirements.txt

@@ -1,5 +1,5 @@
 six
 typing
-requests
+requests<=2.19.1
 python_dateutil
 ask-sdk-model