filters.py: Filter required users

If respond to required users only configuration
is true, then stop responding to users other
than those in the required users list in config.

Fixes coala#515

config.py

@@ -69,6 +69,10 @@
 IGNORE_USERNAMES = os.environ.get("IGNORE_USERNAMES",
                                   'co-robo coala-bot').split()
 
+RESP_ONLY_REQ_USERS = False
+
+REQUIRED_USERS = []
+
 DIVERT_TO_PRIVATE = ('help', )
 
 ROOMS_TO_JOIN = (

utils/filters.py

@@ -23,7 +23,11 @@ def filters(self, msg, cmd, args, dry_run):
         return msg, cmd, args
 
     @cmdfilter
-    def filter_ignored_users(self, msg, cmd, args, dry_run):
-        if msg.frm.nick in self.bot_config.IGNORE_USERNAMES:
+    def filter_users(self, msg, cmd, args, dry_run):
+        name=msg.frm.fullname if BACKEND == 'Zulip' else msg.frm.nick
+        if name in self.bot_config.IGNORE_USERNAMES:
             return None, None, None
-        return msg, cmd, args
+        if (name not in self.bot_config.REQUIRED_USERS
+                and self.bot_config.RESP_ONLY_REQ_USERS):
+            return None, None, None
+        return msg, cmd, args