Issue #20743: Fix a reference leak in test_tcl.

Lib/test/test_tcl.py

@@ -376,6 +376,7 @@ class TclTest(unittest.TestCase):
             result = arg
             return arg
         self.interp.createcommand('testfunc', testfunc)
+        self.addCleanup(self.interp.tk.deletecommand, 'testfunc')
         def check(value, expected, eq=self.assertEqual):
             r = self.interp.call('testfunc', value)
             self.assertIsInstance(result, str)

Misc/NEWS

@@ -117,6 +117,8 @@ IDLE
 Tests
 -----
 
+- Issue #20743: Fix a reference leak in test_tcl.
+
 - Issue #20510: Rewrote test_exit in test_sys to match existing comments,
   use modern unittest features, and use helpers from test.script_helper
   instead of using subprocess directly.  Patch by Gareth Rees.