pip install scikit-learn fails on python 2

[ruoyu90]

Description

pip install scikit-learn fails on python 2

Steps/Code to Reproduce

pip install scikit-learn in a python 2 environment

Expected Results

install succeeds

Actual Results

RuntimeError: Scikit-learn requires Python 3.5 or later. The current Python version is 2.7.16rc1 installed in...

Versions

I expect a lower version to be installed since 0.21 is marked as python 3 only. However the command results in an attempt to install 0.21 and then failure.

[rth]

Thanks for the report @ruoyu90 . Working on a fix in #13861.

Though even once it is fixed, making a new release will not resolve it for python2 users, we might need to remove the 0.20.0 release from PyPi and upload e.g. a 0.20.post0

[ruoyu90]

Thanks! Just verified it works now 👍