Ideogram test for number of chromosomes fails intermittently.

[mkcor]

We've had this CI fail with Python 3.7 over and over again, so there must be a bug:

We want this number of chromosomes to be deterministic.

[mkcor]

Sorry, this intermittent fail also happens with Python 3.6:

[mkcor]

My understanding of test_chromosomes_wrong_input (https://github.com/plotly/dash-bio/blob/master/tests/test_ideogram.py#L297) is that a wrong chromosome name fails silently... Since 'D' isn't valid, it is simply ignored and only '1' and '3' are retained.

[mkcor]

What I've noticed is that, in the screenshots above and CI failures we keep seeing, num_chromosoms actually retained its former value instead of updating as expected. Therefore, I'll try increasing the value of parameter timeout in the wait_for function.

[mkcor]

This other example illustrates the above comment #260 (comment), where the second region wasn't found within 10 seconds (default timeout value):

[mkcor]

Closing for now, because we haven't seen these failures lately (and PR #280, although no silver bullet, may improve things). Will reopen if necessary.