python 2 pip installation fails (incompatible requirements)

[orbeckst]

Expected behavior

1.0 installs with pip under Python 2.7.

Actual behavior

pip install in a clean 2.7 environment (only pip and cython) fails because pip does not seem to be able to select proper packages for the python version. See also issue #2730 .

• joblib (must be < 0.15)
• numpy (must be < 1.17)
• biopython (must be < 1.77)

(at time of issue, more might appear)

Example output

Collecting biopython>=1.71
  Downloading biopython-1.77.tar.gz (16.8 MB)
     |████████████████████████████████| 16.8 MB 29.7 MB/s
    ERROR: Command errored out with exit status 1:
     command: ~/anaconda3/envs/mda2pipX/bin/python2.7 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/ds/z7mbf7nx1gn31308g31t9tcc0000gp/T/pip-install-P2H7xQ/biopython/setup.py'"'"'; __file__='"'"'/private/var/folders/ds/z7mbf7nx1gn31308g31t9tcc0000gp/T/pip-install-P2H7xQ/biopython/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /private/var/folders/ds/z7mbf7nx1gn31308g31t9tcc0000gp/T/pip-pip-egg-info-XjH7zw
         cwd: /private/var/folders/ds/z7mbf7nx1gn31308g31t9tcc0000gp/T/pip-install-P2H7xQ/biopython/
    Complete output (1 lines):
    Biopython requires Python 3.6 or later. Python 2.7 detected.
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

Code to reproduce the behavior

conda create -c conda-forge -n mda2pipX python=2.7 pip cython
conda activate mda2pipX
pip install mdanalysis==1.0.0

Current version of MDAnalysis

• Which version are you using? (run python -c "import MDAnalysis as mda; print(mda.__version__)") 1.0.0
• Which version of Python (python -V)? 2.7
• Which operating system? macOS/conda

[orbeckst]

Fixed in pr #2738