fixup! prettify XML string output by registering default namespace prefixes

Author: spaceone

src/saml2/__init__.py

@@ -572,7 +572,8 @@ def _to_element_tree(self):
         self._add_members_to_element_tree(new_tree)
         return new_tree
 
-    def register_prefix(self, nspair):
+    @staticmethod
+    def register_prefix(nspair):
         """
         Register with ElementTree a set of namespaces
 
@@ -707,7 +708,7 @@ def to_string_force_namespace(self, nspair):
 
         return ElementTree.tostring(elem, encoding="UTF-8")
 
-    def to_string(self, nspair=DEFAULT_NS_PREFIXES):
+    def to_string(self, nspair=None):
         """Converts the Saml object to a string containing XML.
 
         :param nspair: A dictionary of prefixes and uris to use when
@@ -1056,3 +1057,6 @@ def is_required_attribute(cls, attr):
     :return: True if required
     """
     return cls.c_attributes[attr][REQUIRED]
+
+
+SamlBase.register_prefix(DEFAULT_NS_PREFIXES)