Standard tzinfo is not enough for apscheduler

Expected Behavior

apscheduler should work with next_run_time specified with standard tzinfo.

Current Behavior

apscheduler crashes.

Steps to Reproduce

from datetime import datetime, timedelta
from dateutil.tz import tzutc

next_run_time = datetime.now(tzutc()) + timedelta(seconds=30)
scheduler.add_job(
    lambda: print("Hello"), trigger=IntervalTrigger(minutes=1), next_run_time=next_run_time
)

Context (Environment)

apscheduler works only with pytz objects, the problematic call is there : https://github.com/agronholm/apscheduler/blob/18b50d9ee9ff14e816b557e34d7d3abc861d57e5/apscheduler/triggers/interval.py#L66

If next_fire_time is not stamped with a pytz.tzinfo.BaseTzInfo, it crashes.

self.timezone is a pytz object, normalize() is a pytz function which expects a pytz.tzinfo.BaseTzInfo as argument (see https://github.com/stub42/pytz/blob/master/src/pytz/tzinfo.py#L66) with an internal (and absent from the standard tzinfo) _utcoffset there : https://github.com/stub42/pytz/blob/master/src/pytz/tzinfo.py#L252.

[agronholm]

v4.0.0a1 accepts a wider range of tzinfo objects. If you still have trouble, open a new issue against v4.0.0a1.

[agronholm]

It already does, in master.