python: compatibility for python 3.11 (issue6604)

The `unittest._TextTestResult` alias has been removed.
The "new" name has been available since 3.2, and we only support 3.5.3+.

Differential Revision: https://phab.mercurial-scm.org/D11690

tests/basic_test_result.py

@@ -1,9 +1,15 b''
 from __future__ import absolute_import, print_function
 
+import sys
 import unittest
 
+if sys.version_info[0] < 3:
+    base_class = unittest._TextTestResult
+else:
+    base_class = unittest.TextTestResult
 
-class TestResult(unittest._TextTestResult):
+
+class TestResult(base_class):
     def __init__(self, options, *args, **kwargs):
         super(TestResult, self).__init__(*args, **kwargs)
         self._options = options

tests/run-tests.py

@@ -2233,12 +2233,15 b' iolock = threading.RLock()'
 firstlock = threading.RLock()
 firsterror = False
 
-
-class TestResult(unittest._TextTestResult):
+if PYTHON3:
+    base_class = unittest.TextTestResult
+else:
+    base_class = unittest._TextTestResult
+
+
+class TestResult(base_class):
     """Holds results when executing via unittest."""
 
-    # Don't worry too much about accessing the non-public _TextTestResult.
-    # It is relatively common in Python testing tools.
     def __init__(self, options, *args, **kwargs):
         super(TestResult, self).__init__(*args, **kwargs)