tests: Account for argparse bug fix in Python 3.13

Test test_004_enable_opt_mixed is marked as xfail because of an argparse
bug, but the bug is fixed in Python 3.13 so the test unexpectedly
succeeds.  Remove the @unittest.expectedFailure, skip it on Python<3.13,
and add a new tests for older Python that checks for the previous buggy
behavior.

Author: DemiMarie

qubesadmin/tests/tools/qvm_service.py

@@ -20,6 +20,7 @@
 
 # pylint: disable=missing-docstring
 
+import sys
 import unittest
 
 import qubesadmin.tests
@@ -100,7 +101,7 @@ def test_003_enable_opt(self):
             0)
         self.assertAllCalled()
 
-    @unittest.expectedFailure
+    @unittest.skipIf(sys.version_info.minor < 13, reason="argparse bug")
     def test_004_enable_opt_mixed(self):
         self.app.expected_calls[
             ('dom0', 'admin.vm.List', None, None)] = \
@@ -116,6 +117,18 @@ def test_004_enable_opt_mixed(self):
                 0)
         self.assertAllCalled()
 
+    @unittest.skipIf(
+        sys.version_info.minor >= 13, reason="argparse works correctly"
+    )
+    def test_004_enable_opt_mixed_broken(self):
+        with self.assertRaises(SystemExit):
+            self.assertEqual(
+                qubesadmin.tools.qvm_service.main(
+                    ['some-vm', '--enable', 'service1'],
+                    app=self.app),
+                0)
+        self.assertAllCalled()
+
     def test_005_disable(self):
         self.app.expected_calls[
             ('dom0', 'admin.vm.List', None, None)] = \