[commands] Re-order error handler arguments.

They now have Context as the first argument to be consistent with other
context-passing functions.

discord/ext/commands/bot.py

@@ -740,13 +740,13 @@ class BotBase(GroupMixin):
             try:
                 yield from ctx.command.invoke(ctx)
             except CommandError as e:
-                yield from ctx.command.dispatch_error(e, ctx)
+                yield from ctx.command.dispatch_error(ctx, e)
             else:
                 ctx.command_failed = False
                 self.dispatch('command_completion', ctx)
         elif ctx.invoked_with:
             exc = CommandNotFound('Command "{}" is not found'.format(ctx.invoked_with))
-            self.dispatch('command_error', exc, ctx)
+            self.dispatch('command_error', ctx, exc)
 
     @asyncio.coroutine
     def process_commands(self, message):

discord/ext/commands/core.py

@@ -164,7 +164,7 @@ class Command:
         self._after_invoke = None
 
     @asyncio.coroutine
-    def dispatch_error(self, error, ctx):
+    def dispatch_error(self, ctx, error):
         cog = self.instance
         try:
             coro = self.on_error
@@ -173,9 +173,9 @@ class Command:
         else:
             injected = wrap_callback(coro)
             if cog is not None:
-                yield from injected(cog, error, ctx)
+                yield from injected(cog, ctx, error)
             else:
-                yield from injected(error, ctx)
+                yield from injected(ctx, error)
 
         try:
             local = getattr(cog, '_{0.__class__.__name__}__error'.format(cog))
@@ -183,9 +183,9 @@ class Command:
             pass
         else:
             wrapped = wrap_callback(local)
-            yield from wrapped(error, ctx)
+            yield from wrapped(ctx, error)
         finally:
-            ctx.bot.dispatch('command_error', error, ctx)
+            ctx.bot.dispatch('command_error', ctx, error)
 
     def __get__(self, instance, owner):
         if instance is not None: