It looks like the simul test program (https://github.com/llnl/simul) is not installed on some test nodes/distros, so it is being skipped for a large number of test sessions, including full branch landing test sessions:
https://testing.whamcloud.com/search?horizon=518400&test_set_script_id=b10ed7ea-55b4-11e0-bb3d-52540025f9af&sub_test_script_id=b13fa01e-55b4-11e0-bb3d-52540025f9af&source=sub_tests#redirect

It appears that this is related to the distro being tested, but it may also be related to specific test images/nodes missing the package.