unittest: cannot use bytes regexes

[JelleZijlstra]

>>> from unittest.case import TestCase
>>> c = TestCase()
>>> with c.assertRaisesRegex(Exception, b"x"): 1/0
...
ZeroDivisionError: division by zero
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/unittest/case.py", line 274, in __exit__
if not expected_regex.search(str(exc_value)):
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: cannot use a bytes pattern on a string-like object

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[AlexWaygood]

sad, i always wanted to