test_rot13_func in test_codecs is not independent

[serhiy-storchaka]

Bug report

Bug description:

Running separate test test_rot13_func in test_codecs fails:

$ ./python -m test -v test_codecs -m test_rot13_func
...
Traceback (most recent call last):
  File "/home/serhiy/py/cpython/Lib/test/test_codecs.py", line 3572, in test_rot13_func
    encodings.rot_13.rot13(infile, outfile)
    ^^^^^^^^^^^^^^^^
AttributeError: module 'encodings' has no attribute 'rot_13'

CPython versions tested on:

3.11, 3.12, CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-109848: Make test_rot13_func in test_codecs independent #109850
• [3.12] gh-109848: Make test_rot13_func in test_codecs independent (GH-109850) #110504
• [3.11] gh-109848: Make test_rot13_func in test_codecs independent (GH-109850) #110505