Improve changelog

changelog/3632.feature.rst

@@ -1 +1 @@
-Richer comparison introspection on ``AssertionError`` for objects created using `attrs <http://www.attrs.org/en/stable/>`_ or `dataclasses <https://docs.python.org/3/library/dataclasses.html>`_ (Python 3.7+).
+Richer equality comparison introspection on ``AssertionError`` for objects created using `attrs <http://www.attrs.org/en/stable/>`_ or `dataclasses <https://docs.python.org/3/library/dataclasses.html>`_ (Python 3.7+, `backported to Python 3.6 <https://pypi.org/project/dataclasses>`_).

src/_pytest/assertion/util.py

@@ -333,7 +333,7 @@ def _compare_eq_class(left, right, verbose, type=None):
         all_fields = left.__attrs_attrs__
         fields_to_check = [field.name for field in all_fields if field.cmp]
     else:
-        raise RuntimeError
+        raise RuntimeError("Unexpected value for `type` paramater")
 
     same = []
     diff = []