Appveyor constantly failing

[ajdapretnar]

Appveyor is reporting the same issue over and over, even for trivial PRs.
ImportError: cannot import name '__check_build'

Could someone please check, because now most of our tests are failing and it is super annoying.

[ales-erjavec]

This was already fixed in #3139. Old pull requests that failed just need to be rebuild.

[ajdapretnar]

Gotcha.