src/sage/doctest/sources.py: add "long time" for two tests

[orlitzky]

Two calls to FileDocTestSource.create_doctests() in this file can take a while (about 5s) on the first run. This now triggers a "slow doctest" warning if you are unlucky, and is unusually annoying because doctesting this file is expected to produce no output in a doctest in src/sage/doctest/forker.py.

We add # long time to correct that random doctest failure. In any case, the two tests do take a long time.

Fixes

• Flaky test in sage/doctest/forker.py #40661

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[user202729]

if the issue is caused by the first run, it might happen that adding # long time will just push the problem to a later test. Unless this is all the tests there are that tests this code path in this file.

[orlitzky]

if the issue is caused by the first run, it might happen that adding # long time will just push the problem to a later test. Unless this is all the tests there are that tests this code path in this file.

That's exactly what happened. There were only two tests for create_doctests() that use sage.doctest.sources.__file__, though, and I got them both.

[user202729]

Disadvantage is meson regression will go unnoticed, probably.

cf. #40158