add udp to is_url to allow udp trackers

deluge/common.py

@@ -214,7 +214,7 @@ def ftime(seconds):
 def is_url(url):
     """A simple regex test to check if the URL is valid."""
     import re
-    return bool(re.search('^(https?|ftp)://', url))
+    return bool(re.search('^(https?|ftp|udp)://', url))
 
 def is_magnet(uri):
     """Returns True if uri is a valid bittorrent magnet uri."""