hr_schedule - Many places assumes that user has timezone set and if false, exceptions are thrown

[Salton Massally]

Hello Makonnen,

hr_schedule is a great mpdule, though a little daunting to understand. Lovely work...
Anywaz in hr_schedule.py even though I see that some areas take this into consideration, there are still a couple of places where its assumed that the current user has a timezone set. If False and that's passed on to timezone(), an exception is thrown...

please see:
line 308, line 731, line 1020, line 1851, line 712,