I got this test failing on one of the builds:
(http://jenkins.ovirt.org/job/vdsm_master_check-patch-el7-x86_64/5266/console)

09:39:16 ======================================================================
09:39:16 FAIL: testTimeout (storage_iscsi_test.RescanTimeoutTests)
09:39:16 ----------------------------------------------------------------------
09:39:16 Traceback (most recent call last):
09:39:16   File "/home/jenkins/workspace/vdsm_master_check-patch-el7-x86_64/vdsm/tests/monkeypatch.py", line 133, in wrapper
09:39:16     return f(*args, **kw)
09:39:16   File "/home/jenkins/workspace/vdsm_master_check-patch-el7-x86_64/vdsm/tests/monkeypatch.py", line 133, in wrapper
09:39:16     return f(*args, **kw)
09:39:16   File "/home/jenkins/workspace/vdsm_master_check-patch-el7-x86_64/vdsm/tests/storage_iscsi_test.py", line 45, in testTimeout
09:39:16     iscsi.rescan()
09:39:16   File "/usr/lib64/python2.7/contextlib.py", line 24, in __exit__
09:39:16     self.gen.next()
09:39:16   File "/home/jenkins/workspace/vdsm_master_check-patch-el7-x86_64/vdsm/tests/storage_iscsi_test.py", line 33, in assertMaxDuration
09:39:16     (elapsed, maxtime))
09:39:16 AssertionError: Operation was too slow 1.32s > 1.20s
09:39:16 -------------------- >> begin captured logging << --------------------
09:39:16 2016-12-26 09:36:46,857 DEBUG (MainThread) [storage.SamplingMethod] Trying to enter sampling method (vdsm.storage.iscsi.rescan) (misc:467)
09:39:16 2016-12-26 09:36:46,857 DEBUG (MainThread) [storage.SamplingMethod] Got in to sampling method (misc:470)
09:39:16 2016-12-26 09:36:46,857 DEBUG (MainThread) [storage.ISCSI] Performing SCSI scan, this will take up to 1 seconds (iscsi:457)
09:39:16 2016-12-26 09:36:46,858 DEBUG (MainThread) [root] /usr/bin/taskset --cpu-list 0-3 sleep 2 (cwd None) (commands:69)
09:39:16 2016-12-26 09:36:48,183 DEBUG (MainThread) [storage.SamplingMethod] Returning last result (misc:477)
09:39:16 --------------------- >> end captured logging << ---------------------

I was surprised that it uses a time measurement to determine success.

Edy.