https://buildbot.python.org/all/#/builders/145/builds/956 Unhandled exception in thread started by <function Bunch.__init__.<locals>.task at 0x111775cb0> Traceback (most recent call last): File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/lock_tests.py", line 41, in task f() File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/lock_tests.py", line 591, in f self.assertTimeout(dt, 0.1) File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/lock_tests.py", line 80, in assertTimeout self.assertGreaterEqual(actual, expected * 0.6) File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/unittest/case.py", line 1283, in assertGreaterEqual self.fail(self._formatMessage(msg, standardMsg)) File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/unittest/case.py", line 719, in fail raise self.failureException(msg) AssertionError: -0.24049997329711914 not greater than or equal to 0.06 test_waitfor_timeout (test.test_threading.ConditionTests) ... FAIL test_waitfor_timeout(): ... dt = time.time() result = cond.wait_for(lambda : state==4, timeout=0.1) dt = time.time() - dt self.assertFalse(result) self.assertTimeout(dt, 0.1) ... with: def assertTimeout(self, actual, expected): ... self.assertGreaterEqual(actual, expected * 0.6) ... It seems like time.time() gone backward on the buildbot. The test must use time.monotonic() to measure time difference. Attached PR fix the issue.

 New changeset 2cf4c202ffeb30787c944365ba54013688b854c2 by Victor Stinner in branch 'master': bpo-35513: Replace time.time() with time.monotonic() in tests (GH-11182) https://github.com/python/cpython/commit/2cf4c202ffeb30787c944365ba54013688b854c2 

 New changeset be69ff232df23b6ee165d7c34df5435d497cb79b by Miss Islington (bot) in branch '3.7': bpo-35513: Replace time.time() with time.monotonic() in tests (GH-11182) https://github.com/python/cpython/commit/be69ff232df23b6ee165d7c34df5435d497cb79b 

 New changeset 8db5b54463118e5eb60cb3582e3108623f01f5df by Victor Stinner in branch 'master': bpo-35513, unittest: TextTestRunner uses time.perf_counter() (GH-11180) https://github.com/python/cpython/commit/8db5b54463118e5eb60cb3582e3108623f01f5df 

 New changeset 9ade4cbc0f54fc0e2970e4e202f09ab83f5e3b77 by Miss Islington (bot) in branch '3.7': bpo-35513, unittest: TextTestRunner uses time.perf_counter() (GH-11180) https://github.com/python/cpython/commit/9ade4cbc0f54fc0e2970e4e202f09ab83f5e3b77 

I searched from "time.time" and "from time import(...)time" in the Python standard library (in the master branch) and it seems like all usage of time.time() are now appropriate. I close the issue. Sometimes, I'm not sure that if time.monotonic() or time.perf_counter() should be used, but at least both functions are monotonic and so are not affected by this issue (clock going backwards).