Issue #21951: Temporary skip crashing test_user_command on AIX.

diff --cc Lib/test/test_tcl.py
index 5691658643ed6518d591acadf3f4c67831dfd743,e57b5e16bbd7120972843aff8dfac475188ba913..23e7a306729fc2237dceb85b35848d69a801e8d9
--- 1/Lib/test/test_tcl.py
--- 2/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@@ -411,9 -411,8 +411,10 @@@ class TclTest(unittest.TestCase)
              # XXX NaN representation can be not parsable by float()
          self.assertEqual(passValue((1, '2', (3.4,))),
                           (1, '2', (3.4,)) if self.wantobjects else '1 2 3.4')
 +        self.assertEqual(passValue(['a', ['b', 'c']]),
 +                         ('a', ('b', 'c')) if self.wantobjects else 'a {b c}')
  
+     @unittest.skipIf(sys.platform.startswith("aix"), 'Issue #21951: crashes on AIX')
      def test_user_command(self):
          result = None
          def testfunc(arg):