[3.1.x] Refs #30676 -- Added pdb argument to DiscoverRunner docs.

Backport of 2c43840dfb from master

docs/topics/testing/advanced.txt

@@ -510,7 +510,7 @@ behavior. This class defines the ``run_tests()`` entry point, plus a
 selection of other methods that are used to by ``run_tests()`` to set up,
 execute and tear down the test suite.
 
-.. class:: DiscoverRunner(pattern='test*.py', top_level=None, verbosity=1, interactive=True, failfast=False, keepdb=False, reverse=False, debug_mode=False, debug_sql=False, test_name_patterns=None, **kwargs)
+.. class:: DiscoverRunner(pattern='test*.py', top_level=None, verbosity=1, interactive=True, failfast=False, keepdb=False, reverse=False, debug_mode=False, debug_sql=False, test_name_patterns=None, pdb=False, **kwargs)
 
     ``DiscoverRunner`` will search for tests in any file matching ``pattern``.
 
@@ -552,6 +552,9 @@ execute and tear down the test suite.
     ``test_name_patterns`` can be used to specify a set of patterns for
     filtering test methods and classes by their names.
 
+    If ``pdb`` is ``True``, a debugger (``pdb`` or ``ipdb``) will be spawned at
+    each test error or failure.
+
     Django may, from time to time, extend the capabilities of the test runner
     by adding new arguments. The ``**kwargs`` declaration allows for this
     expansion. If you subclass ``DiscoverRunner`` or write your own test
@@ -562,6 +565,10 @@ execute and tear down the test suite.
     custom arguments by calling ``parser.add_argument()`` inside the method, so
     that the :djadmin:`test` command will be able to use those arguments.
 
+    .. versionadded:: 3.0
+
+        The ``pdb`` argument was added.
+
 Attributes
 ~~~~~~~~~~