Workaround cpu detection on Travis CI

[skirpichev]

Closes #316

Not sure if this worth test.

[skirpichev]

This branch used in diofant/diofant#664

[nicoddemus]

Hi @skirpichev,

Thanks for the implementation.

We do need a test though, mostly to avoid future regressions.

Could you also refactor the code inside the if s == "auto": into a separate function, like auto_detect_cpus()? You can more easily test the outcome of that function. We already have some tests in place for that functionality, you can use them as basis for your test.

Thanks again.

[skirpichev]

Ok, done. Not sure, maybe last commit should be squashed with first. Let me know if I should do anything. BTW, tests in diofant/diofant#664 pass too.

[nicoddemus]

Thanks @skirpichev, LGTM!

As soon as we merge this I will prepare a new release.

@RonnyPfannschmidt anything you want to take a look here?

[nicoddemus]

Improved the test a bit to always test the Travis fallback. 👍

[RonnyPfannschmidt]

looks ok, as followup we could take a look at moving the auto-detection tests from acceptance tests to lower integration tests