CIFuzz fails on the 3.13 and 3.14 branches: plistlib parse and LookupError

[vstinner]

Bug report

Examples on a 3.13 PR:

• CIFuzz / python3-libraries (address): https://github.com/python/cpython/actions/runs/28177183993/job/83456696673#logs
• CIFuzz / cpython3 (undefined): https://github.com/python/cpython/actions/runs/28177183993/job/83456696702#logs
• CIFuzz / cpython3 (memory): https://github.com/python/cpython/actions/runs/28177183993/job/83456696797

Example on the address job:

Traceback (most recent call last):
 File "<string>", line 7, in FuzzerRunOne
 File "/github/workspace/build-out/cpython-install/lib/python3.13/plistlib.py", line 925, in loads
 return load(fp, fmt=fmt, dict_type=dict_type, aware_datetime=aware_datetime)
 File "/github/workspace/build-out/cpython-install/lib/python3.13/plistlib.py", line 912, in load
 return p.parse(fp)
 ~~~~~~~^^^^
 File "/github/workspace/build-out/cpython-install/lib/python3.13/plistlib.py", line 194, in parse
 self.parser.ParseFile(fileobj)
 ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
LookupError: unknown encoding: Latin-5_________________________

The artifacts ZIP contains:

<?xml version="2147483646.256" encoding="Latin-5_________________________" ?><svg><svg><svg

cc @StanFromIreland @serhiy-storchaka

[StanFromIreland]

This has now come up a few times, but thankfully the check doesn’t block merges, so there we're not under time pressure to fix this. The larger issue here, however is that the fuzzers are designed to run primarily on OSS Fuzz, which is done against the main branch. CI-Fuzz (which uses the same targets) has been backported all the way to 3.13.

@sethmlarson, since you originally suggested backporting CI-Fuzz, what do you think about reverting that? We could fix the targets to handle the older branches, but I think that's more pain then it's worth. The targets often test internal things and new features, after all. This mismatch is also discussed in python/library-fuzzers#56, but no conclusion has been reached.