[issue41063] Avoid using the locale encoding for open() in tests

[Serhiy Storchaka]

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


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dependencies: +Remove outdated tests for tp_print, pdb reads source files using the locale encoding, read_mime_types() should read the rule file using UTF-8, not the locale encoding

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue41063>
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