pythongh-120544: Add else: fail() to tests where exception is expected (python#120545)

Author: sobolevn

Lib/test/test_exceptions.py

@@ -1859,6 +1859,8 @@ def f():
         except self.failureException:
             with support.captured_stderr() as err:
                 sys.__excepthook__(*sys.exc_info())
+        else:
+            self.fail("assertRaisesRegex should have failed.")
 
         self.assertIn("aab", err.getvalue())
 

Lib/test/test_unittest/test_case.py

@@ -1151,6 +1151,8 @@ def testAssertMultiLineEqual(self):
             # need to remove the first line of the error message
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
+        else:
+            self.fail(f'{self.failureException} not raised')
 
     def testAssertEqualSingleLine(self):
         sample_text = "laden swallows fly slowly"
@@ -1167,6 +1169,8 @@ def testAssertEqualSingleLine(self):
             # need to remove the first line of the error message
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
+        else:
+            self.fail(f'{self.failureException} not raised')
 
     def testAssertEqualwithEmptyString(self):
         '''Verify when there is an empty string involved, the diff output
@@ -1184,6 +1188,8 @@ def testAssertEqualwithEmptyString(self):
             # need to remove the first line of the error message
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
+        else:
+            self.fail(f'{self.failureException} not raised')
 
     def testAssertEqualMultipleLinesMissingNewlineTerminator(self):
         '''Verifying format of diff output from assertEqual involving strings
@@ -1204,6 +1210,8 @@ def testAssertEqualMultipleLinesMissingNewlineTerminator(self):
             # need to remove the first line of the error message
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
+        else:
+            self.fail(f'{self.failureException} not raised')
 
     def testAssertEqualMultipleLinesMismatchedNewlinesTerminators(self):
         '''Verifying format of diff output from assertEqual involving strings
@@ -1227,6 +1235,8 @@ def testAssertEqualMultipleLinesMismatchedNewlinesTerminators(self):
             # need to remove the first line of the error message
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
+        else:
+            self.fail(f'{self.failureException} not raised')
 
     def testEqualityBytesWarning(self):
         if sys.flags.bytes_warning: