This was first found over in Twisted tests.  We probably aren't too terribly worried about it but I wanted to report here anyways.

https://twistedmatrix.com/trac/ticket/9525

Both 3.6 and 3.7 write the same file (sha at the end) based on the script in the first snippet.  3.6 can read both files, 3.7 can't read either.


----
    altendky@lt:~/twisted$ cat ../z.py
    import sys
    import zipfile

    print(sys.version)

    fn = sys.argv[1]
    print(fn)

    with zipfile.ZipFile(fn, 'w') as zf:
        zi = zipfile.ZipInfo("0")
        zi.extra = b"hello, extra"
        zf.writestr(zi, b"the real data")

    zipfile.ZipFile(fn)

----
    altendky@lt:~/twisted$ venv36/bin/python ../z.py 36.zip
    3.6.6 (default, Jul 24 2018, 16:23:12)
    [GCC 6.3.0 20170516]
    36.zip

----
    altendky@lt:~/twisted$ venv37/bin/python ../z.py 37.zip
    3.7.0 (default, Jul  7 2018, 15:49:24)
    [GCC 6.3.0 20170516]
    37.zip
    Traceback (most recent call last):
      File "../z.py", line 14, in <module>
        zipfile.ZipFile(fn)
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 1200, in __init__
        self._RealGetContents()
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 1323, in _RealGetContents
        x._decodeExtra()
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 440, in _decodeExtra
        raise BadZipFile("Corrupt extra field %04x (size=%d)" % (tp, ln))
    zipfile.BadZipFile: Corrupt extra field 6568 (size=27756)

----
    altendky@lt:~/twisted$ cat ../z.py
    import sys
    import zipfile

    print(sys.version)

    fn = sys.argv[1]
    print(fn)

    #with zipfile.ZipFile(fn, 'w') as zf:
    #    zi = zipfile.ZipInfo("0")
    #    zi.extra = b"hello, extra"
    #    zf.writestr(zi, b"the real data")

    zipfile.ZipFile(fn)

----
    altendky@lt:~/twisted$ venv36/bin/python ../z.py 37.zip
    3.6.6 (default, Jul 24 2018, 16:23:12)
    [GCC 6.3.0 20170516]
    37.zip

----
    altendky@lt:~/twisted$ venv37/bin/python ../z.py 36.zip
    3.7.0 (default, Jul  7 2018, 15:49:24)
    [GCC 6.3.0 20170516]
    36.zip
    Traceback (most recent call last):
      File "../z.py", line 14, in <module>
        zipfile.ZipFile(fn)
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 1200, in __init__
        self._RealGetContents()
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 1323, in _RealGetContents
        x._decodeExtra()
      File "/home/altendky/.pyenv/versions/3.7.0/lib/python3.7/zipfile.py", line 440, in _decodeExtra
        raise BadZipFile("Corrupt extra field %04x (size=%d)" % (tp, ln))
    zipfile.BadZipFile: Corrupt extra field 6568 (size=27756)

----
    altendky@lt:~/twisted$ sha256sum 36.zip
    0f54bd6ab84facfeefc2c38f12c30eb84101b3be3d91f8826f6fa36e73b86cb6  36.zip

----
    altendky@lt:~/twisted$ sha256sum 37.zip
    0f54bd6ab84facfeefc2c38f12c30eb84101b3be3d91f8826f6fa36e73b86cb6  37.zip