pep8 fix

Everything passes on my ubuntu vm, but for some strange reason it fails on circle-ci, oh wel...

Author: Jimmy John

src/onelogin/saml2/settings.py

@@ -812,4 +812,4 @@ def is_debug_active(self):
         :returns: Debug parameter
         :rtype: boolean
         """
-        return self.__debug
+        return self.__debug