Add StateHandler to contrib_bots/run.py.

This allows bots to be stateful.  It doesn't handle persistence
after the bot shuts down, but it does store state between
invocations of handle_message.

contrib_bots/lib/followup.py

@@ -37,7 +37,7 @@ class FollowupHandler(object):
 
         return is_follow_up
 
-    def handle_message(self, message, client):
+    def handle_message(self, message, client, state_handler):
         original_content = message['content']
         original_sender = message['sender_email']
         new_content = original_content.replace('@followup',

contrib_bots/lib/help.py

@@ -23,7 +23,7 @@ class HelpHandler(object):
 
         return True
 
-    def handle_message(self, message, client):
+    def handle_message(self, message, client, state_handler):
         help_content = '''
             Info on Zulip can be found here:
             https://github.com/zulip/zulip

contrib_bots/run.py

@@ -42,6 +42,18 @@ def run_message_handler_for_bot(lib_module, quiet, config_file):
 
     message_handler = lib_module.handler_class()
 
+    class StateHandler(object):
+        def __init__(self):
+            self.state = None
+
+        def set_state(self, state):
+            self.state = state
+
+        def get_state(self):
+            return self.state
+
+    state_handler = StateHandler()
+
     if not quiet:
         print(message_handler.usage())
 
@@ -50,7 +62,9 @@ def run_message_handler_for_bot(lib_module, quiet, config_file):
         if message_handler.triage_message(message=message):
             message_handler.handle_message(
                 message=message,
-                client=restricted_client)
+                client=restricted_client,
+                state_handler=state_handler
+                )
 
     logging.info('starting message handling...')
     client.call_on_each_message(handle_message)