Stdout of shell should be decoded with sys.getfilesystemencoding()

[doloopwhile]

Hello.

Errors are raised when $LANG is not utf-8 (ex. LANG=ja_JP.EUCJP).

This cause a bug in pip.
pypa/pip#4917

Would you review it ?

[sethmlarson]

Hey @doloopwhile! Thanks for making this contribution, it looks like a positive change for me.
Currently it looks like our Travis build is failing for unrelated reasons, I'll see if I can fix this. 🎉

[sethmlarson]

Also going to ping @nir0s as this issue should probably mean a new release of distro so that pip can vendor it.