Add `else: fail()` to test cases where exception is always expected

[sobolevn]

Bug report

Most except self.failureClass cases have else branch where we can ensure that the exception really did happen:

cpython/Lib/test/test_unittest/test_case.py

Lines 831 to 837 in d4039d3

	try:
	self.assertSequenceEqual(seq1, seq2)
	except self.failureException as e:
	msg = e.args[0]
	else:
	self.fail('assertSequenceEqual did not fail.')

But, some rare ones do not have them:

cpython/Lib/test/test_unittest/test_case.py

Lines 1148 to 1154 in d4039d3

	try:
	self.assertMultiLineEqual(sample_text, revised_sample_text)
	except self.failureException as e:
	# need to remove the first line of the error message
	error = str(e).split('\n', 1)[1]
	self.assertEqual(sample_text_error, error)

So, in theory they can just succeed and except branch might never be called. This is a theorical problem, but it is still a problem.

I propose to add else branches to these tests, just to be safe.

Linked PRs

• gh-120544: Add else: fail() to tests where exception is expected #120545
• [3.13] gh-120544: Add else: fail() to tests where exception is expected (GH-120545) #120546
• [3.12] gh-120544: Add else: fail() to tests where exception is expected (GH-120545) #120547