[Backport maintenance/4.0.x] Properly detect self.fail() as a terminating node in unittest.TestCase (#10771)

Properly detect 'self.fail()' as a terminating node in 'unittest.TestCase' (#10770)

(cherry picked from commit c45fef7)

Co-authored-by: Zachary Wilkins-Olson <[email protected]>

Author: pylint-backport[bot]

doc/whatsnew/fragments/10743.false_positive

@@ -0,0 +1,3 @@
+Fix possibly-used-before-assignment false positive when using self.fail() in tests.
+
+Closes #10743

pylint/checkers/utils.py

@@ -238,7 +238,13 @@
 SINGLETON_VALUES = {True, False, None}
 
 TERMINATING_FUNCS_QNAMES = frozenset(
-    {"_sitebuiltins.Quitter", "sys.exit", "posix._exit", "nt._exit"}
+    {
+        "_sitebuiltins.Quitter",
+        "sys.exit",
+        "posix._exit",
+        "nt._exit",
+        "unittest.case.TestCase.fail",
+    }
 )
 
 

tests/checkers/unittest_utils.py

@@ -622,3 +622,22 @@ def test_is_reassigned_with_node_no_lineno() -> None:
         assert utils.is_reassigned_before_current(first_assign_name, "x") is False
     finally:
         first_assign_name.lineno = original_lineno
+
+
+def test_is_terminating_func_unittest_fail() -> None:
+    node = astroid.extract_node(
+        """
+    from unittest import TestCase
+    import os
+
+    class TestX(TestCase):
+        def test_foo(self):
+            if 'FOO' in os.environ:
+                x = 1
+            else:
+                self.fail()  #@
+            print(x)
+    """
+    )
+    result = utils.is_terminating_func(node)
+    assert result is True