Move PyPI integration tests into scheduled CI

[robin-nitrokey]

This patch moves the PyPI integration tests into a new workflow that is
executed nightly. (The nightly schedule is chosen to make it easier to
test the configuration. Once we see that everything is working fine, we
could reduce the frequency, for example to weekly builds.)

As discussed in #15.

[daringer]

CI moved to gitlab, so would suggest to drop this and include into the gitlab ci

[daringer]

@LennardBoediger can you please check how to include the currently used tests inside circle CI into gitlab?

[szszszsz]

@LennardBoediger When do you expect to have the CI set up for this project?

[LennardBoediger]

the pipeline for this repo is done
i am just struggling to install lxd on the runner server
If I don't solve the problem today, I will continue to use the test server temporarily so that the CI will definitely be ready today

[szszszsz]

@LennardBoediger can you tell what is the status of this PR?

[szszszsz]

This PR is outdated by solution, since we do not use Circle CI anymore. However the idea is still sound.
@LennardBoediger Are daily builds scheduled for pynitrokey already? If so, please close this ticket with proper comment.

[robin-nitrokey]

I’m closing this PR as the CircleCI configuration is obsolete. I’ve created issue #246 to keep track of the task.