Fix error in validate_signature_fields which prevented signature expiration from being properly evaluated (LP: #2068937)

dkim/__init__.py

@@ -345,10 +345,10 @@ def validate_signature_fields(sig, mandatory_fields=[b'v', b'a', b'b', b'bh', b'
         if x_sign < now - slop:
             raise ValidationError(
                 "x= value is past (%s)" % sig[b'x'])
-            if x_sign < t_sign:
-                raise ValidationError(
-                    "x= value is less than t= value (x=%s t=%s)" %
-                    (sig[b'x'], sig[b't']))
+        if x_sign < t_sign:
+            raise ValidationError(
+                "x= value is less than t= value (x=%s t=%s)" %
+                (sig[b'x'], sig[b't']))
 
 
 def rfc822_parse(message):