[issue45229] Always use unittest for collecting tests in regrtests

[Serhiy Storchaka]

Change by Serhiy Storchaka <storchaka+cpython at gmail.com>:


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dependencies: +Some tests in test_socket are not run, test.test_ssl.TestEnumerations is not run

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45229>
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