Zipimport leaks zlib.error for corrupt deflate data; zstd branch raises ZipImportError

[Tony123-tech]

Bug report

zipimport raises zipimport.ZipImportError when a zstd-compressed
zip entry is corrupt, but leaks zlib.error when a deflate-compressed
entry is corrupt. The two branches of _get_data should behave the
same way, and zipimport's documented contract is that ZipImportError
is the exception raised by zipimporter objects.

Minimal reproducer

import os, sys, zipfile, tempfile, py_compile, importlib, struct

with tempfile.TemporaryDirectory() as d:
    src = os.path.join(d, "mymod.py")
    with open(src, "w") as f:
        f.write("x = 1\n")
    pyc = os.path.join(d, "mymod.pyc")
    py_compile.compile(src, cfile=pyc, doraise=True)

    zp = os.path.join(d, "t.zip")
    with zipfile.ZipFile(zp, "w", compression=zipfile.ZIP_DEFLATED) as z:
        z.write(pyc, "mymod.pyc")     # only .pyc, no .py fallback

    with open(zp, "r+b") as f:
        data = f.read()
        idx = data.find(b"mymod.pyc")
        lh = data.rfind(b"PK\x03\x04", 0, idx)
        name_len, extra_len = struct.unpack_from("<HH", data, lh + 26)
        data_start = lh + 30 + name_len + extra_len
        f.seek(data_start)
        f.write(b"\xff" * 8)

    sys.path.insert(0, zp)
    importlib.invalidate_caches()
    try:
        import mymod
    except Exception as e:
        print(type(e).__module__ + "." + type(e).__name__, e)

Observed

zlib.error Error -3 while decompressing data: invalid block type

Expected

zipimport.ZipImportError could not decompress deflate data

CPython main, commit 77c0675

macOS 15.6 arm64, Clang 17

Linked PRs

• gh-158494: zipimport: raise ZipImportError for corrupt deflate data #158498