Issue #13878: Fix random test_sched failures.

diff --cc Lib/test/test_sched.py
index ae82f94053e07db1dd6fd16e14203cda609a889f,91b8f0c939deca2781d4a174c6a7318198ad0335..50ada522a2694f9d366eaff9014a98938335b6f1
--- 1/Lib/test/test_sched.py
--- 2/Lib/test/test_sched.py
+++ b/Lib/test/test_sched.py
@@@ -62,38 -63,15 +63,39 @@@ class TestCase(unittest.TestCase)
  
      def test_queue(self):
          l = []
 -        events = []
          fun = lambda x: l.append(x)
          scheduler = sched.scheduler(time.time, time.sleep)
-         e5 = scheduler.enter(0.05, 1, fun)
-         e1 = scheduler.enter(0.01, 1, fun)
-         e2 = scheduler.enter(0.02, 1, fun)
-         e4 = scheduler.enter(0.04, 1, fun)
-         e3 = scheduler.enter(0.03, 1, fun)
 -        self.assertEqual(scheduler._queue, [])
 -        for x in [0.05, 0.04, 0.03, 0.02, 0.01]:
 -            events.append(scheduler.enterabs(x, 1, fun, (x,)))
 -        self.assertEqual(scheduler._queue.sort(), events.sort())
++        now = time.time()
++        e5 = scheduler.enterabs(now + 0.05, 1, fun)
++        e1 = scheduler.enterabs(now + 0.01, 1, fun)
++        e2 = scheduler.enterabs(now + 0.02, 1, fun)
++        e4 = scheduler.enterabs(now + 0.04, 1, fun)
++        e3 = scheduler.enterabs(now + 0.03, 1, fun)
 +        # queue property is supposed to return an order list of
 +        # upcoming events
 +        self.assertEqual(list(scheduler.queue), [e1, e2, e3, e4, e5])
 +
 +    def test_args_kwargs(self):
 +        flag = []
 +
 +        def fun(*a, **b):
 +            flag.append(None)
 +            self.assertEqual(a, (1,2,3))
 +            self.assertEqual(b, {"foo":1})
 +
 +        scheduler = sched.scheduler(time.time, time.sleep)
 +        z = scheduler.enterabs(0.01, 1, fun, argument=(1,2,3), kwargs={"foo":1})
          scheduler.run()
 -        self.assertEqual(scheduler._queue, [])
 +        self.assertEqual(flag, [None])
 +
 +    def test_run_non_blocking(self):
 +        l = []
 +        fun = lambda x: l.append(x)
 +        scheduler = sched.scheduler(time.time, time.sleep)
 +        for x in [10, 9, 8, 7, 6]:
 +            scheduler.enter(x, 1, fun, (x,))
 +        scheduler.run(blocking=False)
 +        self.assertEqual(l, [])
  
  
  def test_main():