firewall: use IPAddress.words instead of regex matching in convert_ipv4_to_ipv6()

circle/firewall/fields.py

@@ -263,10 +263,8 @@ def val_mx(value):
 
 def convert_ipv4_to_ipv6(ipv6_template, ipv4):
     """Convert IPv4 address string to IPv6 address string."""
-    ipv4 = str(ipv4)
-    val_ipv4(ipv4)
-    m = ipv4_re.match(ipv4)
-    return IPAddress(ipv6_template % {'a': int(m.group(1)),
-                                      'b': int(m.group(2)),
-                                      'c': int(m.group(3)),
-                                      'd': int(m.group(4))})
+    m = ipv4.words
+    return IPAddress(ipv6_template % {'a': int(m[0]),
+                                      'b': int(m[1]),
+                                      'c': int(m[2]),
+                                      'd': int(m[3])})