Reduce duplication

Subtraction is just adding a negative value

karma.py

@@ -35,13 +35,8 @@ class Karma(BotPlugin):
 
         super().deactivate()
 
-    def _inc_karma(self, target, message):
-        self.karma[target] += 1
-        text = "Karma for '{}' is now {}".format(target, self.karma[target])
-        self.send(message.to, text, message, True)
-
-    def _dec_karma(self, target, message):
-        self.karma[target] -= 1
+    def _change_karma(self, target, value, message):
+        self.karma[target] += value
         text = "Karma for '{}' is now {}".format(target, self.karma[target])
         self.send(message.to, text, message, True)
 
@@ -49,12 +44,12 @@ class Karma(BotPlugin):
         # Increment?
         match = self.inc.search(message.body)
         if match:
-            self._inc_karma(match.group(1), message)
+            self._change_karma(match.group(1), 1, message)
 
         # Decrement?
         match = self.dec.search(message.body)
         if match:
-            self._dec_karma(match.group(1), message)
+            self._change_karma(match.group(1), -1, message)
 
     @botcmd
     def karma_list(self, message, args):
@@ -71,7 +66,7 @@ class Karma(BotPlugin):
         if not args:
             return "**Usage**: !karma add <target>"
 
-        self._inc_karma(args, message)
+        self._change_karma(args, 1, message)
 
     @botcmd
     def karma_remove(self, message, args):
@@ -79,7 +74,7 @@ class Karma(BotPlugin):
         if not args:
             return "**Usage**: !karma remove <target>"
 
-        self._dec_karma(args, message)
+        self._change_karma(args, -1, message)
 
     @botcmd
     def karma(self, message, args):