Run the unit tests every time

[texasaggie97-zz]

[X] This contribution adheres to [CONTRIBUTING.md]

What does this Pull Request accomplish?

• This is not invoking tox, just run a quick pytest on the generated files
• Fixes Unit tests aren't re-run if they fail in next make #124

Why should this Pull Request be merged?

• Fixes issue

What testing has been done?

• Travis
• Building multiple time under different circumstances

[marcoskirsch]

So this fixed the issue, but introduces a new issue (tests run when not necessary).
The new issue is more benign than the original.

Do you want to merge this and we open a new issue, or do you want to try and get it to work right?

[texasaggie97-zz]

I prefer to merge this and start another issue about building too much. Wheels also build every time.