Only install packages for current python version

[techalchemy]

• Still resolve all packages to lockfile
• Fixes Note in documentation about broken Python 2.7.12 and Virtualenv installation on Ubuntu 16.04 #1952, Pipfile python_version not taken into account when generating lockfile #1901

Signed-off-by: Dan Ryan dan@danryan.co

[techalchemy]

I haven’t really considered all the implications of this and would appreciate input from @vphilippon

[kennethreitz]

I'm skeptical of this.

[techalchemy]

me too.

[techalchemy]

Todo:

• Test against private indexes / ensure hashes come through properly
• Ensure that we retain markers where we can actually drop them through / there is one version for a different python version

[kennethreitz]

i don't think we should change this, at this time.

[kennethreitz]

if we have marker problems, we need to resolve those instead.

[techalchemy]

I agree and I actually think I have a fix for this, will PR it in a bit