Added changelog about the --pdb fix

Author: pelme

docs/changelog.rst

@@ -1,6 +1,20 @@
 Changelog
 =========
 
+3.1.1
+-----
+
+Bug fixes
+^^^^^^^^^
+
+* Workaround `--pdb` interaction with Django TestCase. The issue is caused by
+  Django TestCase not implementing TestCase.debug() properly but was brought to
+  attention with recent changes in pytest 3.0.2. Related issues:
+  * https://github.com/pytest-dev/pytest/issues/1977
+  * https://github.com/pytest-dev/pytest-django/pull/406
+  * https://code.djangoproject.com/ticket/27391
+
+
 3.1.0
 -----