implement environment markers to fix poetry

[fishman]

pep 508 recommends the usage of environment markers rather than version_info
https://www.python.org/dev/peps/pep-0508/#environment-markers

currently installing using poetry resolves the wrong libraries

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[fishman]

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[fishman]

@edenhill can we get this merged? It breaks pretty much all python 3.6/3.7 installs by installing enum34 on an unsupported platform. It also goes against https://www.python.org/dev/peps/pep-0508/#environment-markers

It's a non intrusive change that fixes a lot of environments. python-poetry/poetry#844 (comment)

[edenhill]

Awesome, thank you!

[fishman]

@edenhill is there any chance you can do a 1.0.1 service release ? right now i still have to manually remove enum34 after installing anywhere i use poetry

[edenhill]

We're aiming to do a 1.0.1 maintenance release (with this fix and other ones) within a couple of weeks.