*(minor): small refactor

passbook/providers/saml/exceptions.py

@@ -0,0 +1,9 @@
+"""passbook SAML IDP Exceptions"""
+
+
+class CannotHandleAssertion(Exception):
+    """This processor does not handle this assertion."""
+
+
+class UserNotAuthorized(Exception):
+    """User not authorized for SAML 2.0 authentication."""