Update Python versions

[hugovk]

And add python_requires to help pip.

Latest master fails on the old 2.7 on Appveyor: https://ci.appveyor.com/project/hugovk/cycler/build/1.0.1

[Kojoley]

Is PYTHON_VERSION and PYTHON_ARCH used anywhere?

[hugovk]

Yes, they're used by https://github.com/matplotlib/cycler/blob/master/ci/appveyor/install.ps1

[Kojoley]

You are right... then a path you defined for 3.6 interfere with appveyor installed python.

[hugovk]

Which line interferes?

At least AppVeyor passes: https://ci.appveyor.com/project/hugovk/cycler/build/1.0.4

By the way, should AppVeyor be enabled for this repo? Then you get builds for PRs on AppVeyor and Travis.

[Kojoley]

Which line interferes?

Appveyor has installed python under C:\Python36-x64 path https://www.appveyor.com/docs/build-environment/#python.
Actually I do not know why we are downloading and installing the python. It looks unnecessary to me.

By the way, should AppVeyor be enabled for this repo?

@tacaswell could you please enable appveyor on organization account for cycler? It looks like I can't do it myself.

[hugovk]

I'm not sure Why Python is downloaded rather then using the existing versions, but I bet there was a good reason. Maybe a specific version was needed. Does @tacaswell know?

Should we try it out with the system Pythons?

[codecov-io]

Codecov Report

Merging #43 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #43   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines         177    177           
  Branches       50     50           
=====================================
  Hits          177    177

---

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[tacaswell]

power-cycled to see if appveyor will fire.

Those old build failures look like dependency issues (missing setuptools) rather than cycler not working with old versions of 2.7.

[tacaswell]

ohh, sorry, not reading the urls clearly (@hugovk 's account above and the emails I got from appveyor were tied to my personal account not matplotlib's). I'll see if I can sort this out when not on tethered-to-phone internet.

[Kojoley]

Those old build failures look like dependency issues (missing setuptools) rather than cycler not working with old versions of 2.7.

Yeah, cycler uses python setup.py install, so setuptools should have been installed before calling it.

[hugovk]

Is there anything I can do to move this closer to merge?

[tacaswell]

https://ci.appveyor.com/project/matplotlib/cycler appveyor should be active now

[tacaswell]

'power cycled' again to trigger appveyor.

No good reason to not use the system python. This appevyor configuration file was cargo-cult-ed from matplotlib/matplotlib which needs to compile c/c++. It can probably be greatly simplified.

[Kojoley]

@hugovk I have rebased and forcepushed to your branch.

[tacaswell]

I am quite happy that this is a -250 line PR

[tacaswell]

Thanks @Kojoley and @hugovk !