Hi, 

in the code given below, the last assert fails
when running with 
/mingw64/bin/python3 (Python 3.7.0 -- mingw64's python3 from msys2 project)
C:\Python36\python.exe (Python 3.6.6 -- windows installer)

It does not fail when running with
/usr/bin/python3 (Python 3.6.6 -- msys's python3 from msys2 project)






import sched, time, threading

class A(threading.Thread):
    def __init__(self, sched):
        threading.Thread.__init__(self)
        self._sched = sched
        self.start()

    def run(self):
        self._sched.run()




s = sched.scheduler(time.monotonic, time.sleep)

ev1=None
def go1(a=''):
    print(a)
    global ev1
    ev1 = s.enterabs(time.monotonic()+1, 1, go1, argument=('a',))

ev2=None 
def go2(a=''):
    print(a)
    global ev2
    ev2 = s.enterabs(time.monotonic()+1, 1, go2, argument=('b',))


ev1 = s.enterabs(time.monotonic()+1, 1, go1, argument=('a',))
ev2 = s.enterabs(time.monotonic()+1, 1, go2, argument=('b',))
a = A(s)
time.sleep(2.5)
print('schedu queue before', s.queue)
assert 1 == 1
print('remove', ev2)
assert ev2 in s.queue
s.cancel(ev2)
print('schedu queue after', s.queue)
assert ev2 not in s.queue   # fails (SOMETIMES)


# what is going on here???
# does the last assert also fail from anybody else?