Raise useful exception when called with URL for which request type

cannot be determined.

Pseudo-fix for SF bug #420724

Lib/urllib2.py

@@ -217,7 +217,8 @@ def get_full_url(self):
     def get_type(self):
         if self.type is None:
             self.type, self.__r_type = splittype(self.__original)
-            assert self.type is not None, self.__original
+            if self.type is None:
+                raise ValueError, "unknown url type: %s" % self.__original
         return self.type
 
     def get_host(self):