add stacklevel=2 in warning calls (flake8-bugbear's B028)

Author: g-as

djangosaml2/backends.py

@@ -322,27 +322,31 @@ def get_attribute_value(self, django_field, attributes, attribute_mapping):
         warnings.warn(
             "get_attribute_value() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return self._get_attribute_value(django_field, attributes, attribute_mapping)
 
     def get_django_user_main_attribute(self):
         warnings.warn(
             "get_django_user_main_attribute() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return self._user_lookup_attribute
 
     def get_django_user_main_attribute_lookup(self):
         warnings.warn(
             "get_django_user_main_attribute_lookup() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return getattr(settings, "SAML_DJANGO_USER_MAIN_ATTRIBUTE_LOOKUP", "")
 
     def get_user_query_args(self, main_attribute):
         warnings.warn(
             "get_user_query_args() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return {
             self.get_django_user_main_attribute()
@@ -353,20 +357,23 @@ def configure_user(self, user, attributes, attribute_mapping):
         warnings.warn(
             "configure_user() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return self._update_user(user, attributes, attribute_mapping)
 
     def update_user(self, user, attributes, attribute_mapping, force_save=False):
         warnings.warn(
             "update_user() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return self._update_user(user, attributes, attribute_mapping)
 
     def _set_attribute(self, obj, attr, value):
         warnings.warn(
             "_set_attribute() is deprecated, look at the Saml2Backend on how to subclass it",
             DeprecationWarning,
+            stacklevel=2,
         )
         return set_attribute(obj, attr, value)
 
@@ -375,5 +382,6 @@ def get_saml_user_model():
     warnings.warn(
         "_set_attribute() is deprecated, look at the Saml2Backend on how to subclass it",
         DeprecationWarning,
+        stacklevel=2,
     )
     return Saml2Backend()._user_model