selenium testing

[fisx]

• script for running the docker selenium executable.
• trivial test case (everything else can come later).

[fisx]

• currently depends on branch aula-docker-0.2, but i want to merge that branch and revert the resp. commit before landing this PR.

issues

quay.io seems to have a hard time building today. haven't investigated yet.

building the docker image locally might work (i only tried by hand), but running the test suite fails. i have tried firefox and chromium with similar error messages (grid cannot connect to driver). the problem definitely lies on the selenium side (the browser cannot be started), but other than that i have mostly walked through dead ends.

[fisx]

quay.io has recovered.

[fisx]

the issue was that chrome doesn't like to run with sandboxes inside docker (something about linux containers inside containers). didn't resolve the firefox issue; chrome works fine now.

[fisx]

to merge the two branches in aula-docker and here, proceed as follows:

1. merge this branch.
2. revert the branch pinning commit on aula-docker-0.2.
3. merge aula-docker-0.2.
4. revert the branch pinning commit on this branch.
5. merge this branch again.

(2, 3, 4, 5 can be done locally and pushed to github when done; 4, 5 need to happen after quay.io image tag master has been updated.)

[fisx]

(updated last comment.)

[fisx]

See #907 for a more developed version of the above process.

[andorp]

So far so good.