add changelog entry and documentation note about RecordedWarning

CHANGELOG.rst

@@ -28,6 +28,9 @@ Changes
   to ``io.UnsupportedOperation``. Thanks `@vlad-dragos`_ for the PR.
 
 
+* fix `#2013`_: turn RecordedWarning into namedtupe,
+  to give it a comprehensible repr while preventing unwarranted modification
+
 .. _@davidszotten: https://github.com/davidszotten
 .. _@fushi: https://github.com/fushi
 .. _@mattduck: https://github.com/mattduck
@@ -35,6 +38,7 @@ Changes
 .. _#1512: https://github.com/pytest-dev/pytest/issues/1512
 .. _#1874: https://github.com/pytest-dev/pytest/pull/1874
 .. _#1952: https://github.com/pytest-dev/pytest/pull/1952
+.. _#2013: https://github.com/pytest-dev/pytest/issues/2013
 
 
 3.0.4.dev

doc/en/recwarn.rst

@@ -92,6 +92,9 @@ Each recorded warning has the attributes ``message``, ``category``,
 class of the warning. The ``message`` is the warning itself; calling
 ``str(message)`` will return the actual message of the warning.
 
+.. note::
+    :class:`RecordedWarning` was changed from a plain class to a namedtuple in pytest 3.1
+
 .. note::
     ``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
     differently; see :ref:`ensuring_function_triggers`.