Demo built-in-meshes fails on python 3 buildbot

[Martin Sandve Alnæs]

The py3 buildbot consistently fails on the built-in-meshes demo:

http://fenicsproject.org:8010/builders/dolfin-next-full-trusty-amd64-py3/builds/407/steps/make%20run_regressiontests/logs/stdio


----------------------------------------------------------------------
Running Python demo ./../../demo/documented/built-in-meshes/python
command timed out: 1200 seconds without output, attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2050.595538

[Jan Blechta]

Another built got stuck elsewhere.

@johannes_ring, are we running CPython unbuffered by python -u or export PYTHONUNBUFFERED=1? Buffering could spoil the 1200 seconds check. It might also be the reason of frequent failures of book tests (there is maybe a lot of actual testing and a few of output).

[Martin Sandve Alnæs]

I can add a flush to the gc fixture.

[Johannes Ring]

No, we are not running with python -u or export PYTHONUNBUFFERED=1 on the buildbots. Should we?

[Jan Blechta]

I'd say so. Maybe export PYTHONUNBUFFERED=1 is the best as test/regression/test.py spawns new python processes. Not sure how unit tests are executed but python executable should again read that env variable.

[Martin Sandve Alnæs]

Unit tests are run as described in CMakeFiles.txt with 'python -B -m pytest', adding -u there shouldn't be a problem.

[Jan Blechta]

Attempt to fix the problem by using unbuffered interpreter e57c7bc.

[Jan Blechta]

e57c7bc did not do the job.

[Jan Blechta]

Duplicate of #476.

[Martin Sandve Alnæs]

Removing milestone: 1.6 (automated comment)