Update autoauth.py

Correct weechat#605 
Correction found by @flashcode , verified by me

Author: crazycatdevs

python/autoauth.py

@@ -301,7 +301,7 @@ def get_channel_from_buffer_args(buffer, args):
     if not channel_name:
         channel_name = weechat.buffer_get_string(buffer, "localvar_channel")
 
-    match_data = re.match("\A(irc.)?([^.]+)\.(#\S+)\Z", channel_name)
+    match_data = re.match(r"\A(irc.)?([^.]+)\.(#\S+)\Z", channel_name)
     if match_data:
         channel_name = match_data.group(3)
         server_name = match_data.group(2)