fix call to is_market_open when using the new exchange_calendars

Author: camelpac

alpaca_backtrader_api/alpacastore.py

@@ -445,7 +445,7 @@ def _make_sure_dates_are_initialized_properly(self, dtbegin, dtend,
               not dtend.tzname() else dtend
         if granularity == Granularity.Minute:
             calendar = exchange_calendars.get_calendar(name='NYSE')
-            while not calendar.is_open_on_minute(dtend):
+            while not calendar.is_open_on_minute(dtend.ceil(freq='T')):
                 dtend = dtend.replace(hour=15,
                                       minute=59,
                                       second=0,