cftime 1.5.2 breaks Python 2.7 compatibility

[dtasev]

To report a non-security related issue, please provide:

• the version of the software with which you are encountering an issue: cftime 1.5.2 (released 22 January 2022)
• environmental information (i.e. Operating System, compiler info, java version, python version, etc.)
  • Python 2.7
  • Debian GNU/Linux 10 (buster) & openSUSE Leap 42.3
• a description of the issue with the steps needed to reproduce it:

Easiest way to test it is docker: docker run -it python:2.7 pip install cftime==1.5.2, producing:

$ docker run -e HTTP_PROXY -e HTTPS_PROXY -it python:2.7 pip install cftime==1.5.2     30.7s  Mon 24 Jan 2022 12:11:07 GMT
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Collecting cftime==1.5.2
  Downloading cftime-1.5.2.tar.gz (46 kB)
     |████████████████████████████████| 46 kB 517 kB/s 
  Installing build dependencies ... error
  ERROR: Command errored out with exit status 1:
   command: /usr/local/bin/python /usr/local/lib/python2.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-4aB4aV/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=41.2' cython wheel oldest-supported-numpy
       cwd: None
  Complete output (11 lines):
  DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
  Collecting setuptools>=41.2
    Downloading setuptools-44.1.1-py2.py3-none-any.whl (583 kB)
  Collecting cython
    Downloading Cython-0.29.26-cp27-cp27mu-manylinux_2_5_x86_64.manylinux1_x86_64.whl (1.9 MB)
  Collecting wheel
    Downloading wheel-0.37.1-py2.py3-none-any.whl (35 kB)
  ERROR: Could not find a version that satisfies the requirement oldest-supported-numpy (from versions: none)
  ERROR: No matching distribution found for oldest-supported-numpy
  WARNING: You are using pip version 20.0.2; however, version 20.3.4 is available.
  You should consider upgrading via the '/usr/local/bin/python -m pip install --upgrade pip' command.
  ----------------------------------------
ERROR: Command errored out with exit status 1: /usr/local/bin/python /usr/local/lib/python2.7/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-4aB4aV/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=41.2' cython wheel oldest-supported-numpy Check the logs for full command output.

Obviously, Python 2.7 issue, not really expecting a fix and pinning to cftime==1.5.1.1 fixed our builds.

Just making you aware, as https://pypi.org/project/cftime/ still claims Python 2.7 support.

Honestly, I can't even track down what exactly caused this, as the only changes to requirements.txt that I can see are that numpy is now pinned to 1.13, which should be fine as cftime==1.5.1.1 installs numpy==1.16 anyway.

Another behaviour difference I see is in the packages that are installed during pip:

cftime==1.5.1.1 produces:

$ pip install "cftime<1.5.2"
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Collecting cftime<1.5.2
  Downloading cftime-1.5.1.1.tar.gz (46 kB)
     |████████████████████████████████| 46 kB 737 kB/s 
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Collecting numpy
  Using cached numpy-1.16.6-cp27-cp27mu-manylinux1_x86_64.whl (17.0 MB)
Building wheels for collected packages: cftime
  Building wheel for cftime (PEP 517) ... done
  Created wheel for cftime: filename=cftime-1.5.1.1-cp27-cp27mu-linux_x86_64.whl size=666016 sha256=63e8c0b3921f9bda68bb6d4a6ea9b99f45a3fb96bc0811979ef545bd4dd550f1
  Stored in directory: /root/.cache/pip/wheels/fe/47/b7/5557025e16396c30079301e9ec609b3cae54c38a430576c4fb
Successfully built cftime
Installing collected packages: numpy, cftime
Successfully installed cftime-1.5.1.1 numpy-1.16.6

while cftime==1.5.2 pulls in cython wheel and oldest-supported-numpy. I can't tell what causes the extra packages, but will dig in some more to see if I come up with some idea, as they are only found in requirements-dev.txt!