Please yank 4.21.0 which pip installs for Python versions < 3.7

[jtfung]

Apologies if this is the wrong place for this issue ...

I tried installing the latest version of protobuf after it was released yesterday, hoping that the latest version fixes a problem where an incompatible 4.21.0 (which is missing metadata and/or attributes, I don't know which) gets installed on Python versions < 3.7. No luck.

Here is a failed attempt to install a "compatible" version with Python 3.6.x:

$ date
Sat May 28 22:11:23 MDT 2022

$ python --version
Python 3.6.9

$ pip --version
pip 21.3.1 from ...

$ pip install --no-cache-dir protobuf
Collecting protobuf
...
Successfully installed protobuf-4.21.0

Here's a successful attempt to install a compatible versions with Python 3.8.x (I would expect the same result with Python >= 3.7x):

$ date
Sat May 28 21:15:21 PDT 2022

$ python --version
Python 3.8.12

$ pip --version
pip 21.1.1 from ...

$ pip install --no-cache-dir protobuf
Collecting protobuf
...
Successfully installed protobuf-4.21.1

Please yank 4.21.0! Thank you.

[zifban]

I second this. Please (re-)yank 4.21.0. The code there uses f-strings that are not supported by Python 3.5.

How to replicate:

$ docker run --rm -it python:3.5 /bin/bash
# pip install -q -U pip
# pip install -q protobuf
# pip list
Package    Version
---------- -------
pip        20.3.4
protobuf   4.21.0
setuptools 50.3.0
wheel      0.35.1
# python -c 'import google.protobuf.reflection'
...
    from google.protobuf.internal import containers
  File "/usr/local/lib/python3.5/site-packages/google/protobuf/internal/containers.py", line 349
    f'{self.__class__.__name__} object does not support item assignment')
                                                                       ^
SyntaxError: invalid syntax

[zhangskz]

Thanks for bringing this up -- we've yanked 4.21.0.

We believe this should no longer be an issue in 4.21.1 per #10053