It is more a matter of tradeoffs rather than 'okay'.

There is no general pydev rule against gui flashing.  The tk and ttk gui tests still do, but that is primarily Serhiy's concern.

The IDLE tests are at most perhaps a third complete, so they would have become collectively 3 or more times worse.  I should run the IDLE tests at least once for each patch and usually do it multiple times.  When I work on a module or its tests, I tend work incrementally and run the test for the module 10 or 20 times or more.  So my first concern is my own eyes and mental state.

Second, I plan to ask others to run test_idle to make up for the lack of buildbot coverage, and I will feel better about doing so after the patches already made.  If one or a few flashes are left, I and others are still much better off.

In this case, there are two obvious fixes, but I don't like either.  Maybe I will come up with a third I like better, perhaps after some refactoring of the module.  I would also like to better understand the detailed behavior.  In the meanwhile, I reopened to add a comment to the test, so I don't lose track of the source of the remaining flash.