Fix CryptoBackendXMLSecurity.validate_signature.

The validate_signature method is called with the parameters
named, so it does not work to rename the parameters from the
names used in the superclass.

Author: fredrikt

src/saml2/sigver.py

@@ -855,8 +855,8 @@ def sign_statement(self, statement, _class_name, key_file, node_id,
         signed = xmlsec.sign(xml, key_file)
         return lxml.etree.tostring(signed, xml_declaration=True)
 
-    def validate_signature(self, signedtext, cert_file, cert_type, _node_name,
-                           _node_id, _id_attr):
+    def validate_signature(self, signedtext, cert_file, cert_type, node_name,
+                           node_id, id_attr):
         """
         Validate signature on XML document.