Arvados

Very occasionally, a Python tool will say on stderr as it exits:

close failed in file object destructor:
sys.excepthook is missing
lost sys.stderr

I'm not sure we've ever observed it in the wild, but it occasionally causes test failures on Jenkins. For an example, see the TestCrunchJob#test_fail_clean_tmp failure in this console.

Track down where this is coming from, and fix it.