Update HTTP workflow action to new requests API

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -277,6 +277,7 @@
   clarity.
 * Add note about the new preparestatic command.
 * Add no-result template for workflow instance detail view.
+* Update HTTP workflow action to new requests API.
 
 3.1.11 (2019-04-XX)
 ===================

mayan/apps/document_states/workflow_actions.py

@@ -166,4 +166,4 @@ class HTTPPostAction(WorkflowAction):
 
         logger.debug('payload json result: %s', payload)
 
-        requests.post(url=url, data=payload, timeout=self.form_data['timeout'])
+        requests.post(url=url, json=payload, timeout=self.form_data['timeout'])