Issue #24134: assertRaises(), assertRaisesRegex(), assertWarns() and

assertWarnsRegex() checks are not longer successful if the callable is None.

Added tests for assertRaises().

diff --cc Lib/unittest/test/test_case.py
Simple merge

diff --cc Misc/NEWS
index 0b47d8a3248f545a9773b46027f6ca21b51785ec,333aa43d889f0f16d8279f48c1627d69fe6a723d..336038beba0b5806ba3b4c0dc0b6547f13c40323
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -30,12 -42,9 +30,15 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #24134: assertRaises(), assertRaisesRegex(), assertWarns() and
+   assertWarnsRegex() checks are not longer successful if the callable is None.
+ 
 +- Issue #23880: Tkinter's getint() and getdouble() now support Tcl_Obj.
 +  Tkinter's getdouble() now supports any numbers (in particular int).
 +
 +- Issue #22619: Added negative limit support in the traceback module.
 +  Based on patch by Dmitry Kazakov.
 +
  - Issue #24094: Fix possible crash in json.encode with poorly behaved dict
    subclasses.