Make core compatible with pendulum 3

[Taragolis]

In pendulum 3 (beta) there is no access to pendulum.tz.timezone anymore otherwise we should call pendulum.timezone for convert string/integer to pendulum timezones

>>> import pendulum
>>> pendulum.__version__
'2.1.2'

>>> pendulum.tz.timezone("UTC")
Timezone('UTC')
>>> pendulum.tz.timezone("Europe/London")
Timezone('Europe/London')
>>> pendulum.tz.timezone(3600)
Timezone('+01:00')

>>> pendulum.timezone("UTC")
Timezone('UTC')
>>> pendulum.timezone("Europe/London")
Timezone('Europe/London')
>>> pendulum.timezone(3600)
Timezone('+01:00')

>>> import pendulum
>>> pendulum.__version__
'3.0.0b1'

>>> pendulum.tz.timezone("UTC")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'module' object is not callable
>>> pendulum.tz.timezone("Europe/London")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'module' object is not callable

>>> pendulum.timezone("UTC")
Timezone('UTC')
>>> pendulum.timezone("Europe/London")
Timezone('Europe/London')
>>> pendulum.timezone(3600)
FixedTimezone(3600, name="+01:00")

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[uranusjr]

Generally lgtm, just a couple of nits

[bolkedebruin]

Some questions and small nits. Generally looks fine, thanks for putting in the work.

[bolkedebruin]

is there an issue moving to Pendulum 3 UTC? So moving from FixedTimezone to Timezone? FixedTimezone derives from Timezone.

[Taragolis]

That is interesting question. In general speaking right now we use two different version of UTC timezone in airflow codebase.

1. FixedTimezone created by pendulum.tz.timezone("UTC") in most part of codebase
2. Timezone created by pendulum.tz.timezone.Timezone("UTC") in timetables

This is a two different objects with different attributes however it should work exactly the same. So it might be a good idea to try to resolve different implementation of UTC timezone in airflow codebase, I just choose to keep the same as it now in most parts, but I happy to change it to pendulum.tz.timezone.Timezone("UTC")

[Taragolis]

@bolkedebruin
Well as we could see on our CI Timezone("UTC") in pendulum 2.x might not work into some specific cases such

airflow/airflow/example_dags/plugins/workday.py

Lines 51 to 52 in 5623575

	else:
	holidays = holiday_calendar.holidays(start=next_start, end=next_start).to_pydatetime()

This code works fine in pendulum 3, however it failed (or spawn a lot of warnings) in 2.1.2

from pendulum.tz.timezone import FixedTimezone, Timezone
from datetime import datetime
from pandas.tseries.holiday import USFederalHolidayCalendar

holiday_calendar = USFederalHolidayCalendar()

for utc in [FixedTimezone(offset=0, name="UTC"), Timezone("UTC")]:
    print(f" {utc} {type(utc).__name__} ".center(72, "="))
    next_start = datetime(2021, 9, 5, tzinfo=utc)
    result = holiday_calendar.holidays(start=next_start, end=next_start)
    print(f"Result: {next_start}")

[Taragolis]

And revert it back to FixedTimezone

[bolkedebruin]

and what about using

from datetime import timezone

utc = timezone.utc

[Taragolis]

Need to check this one, some of the methods pendulum 2 have a problem with non-pendulum's timezones, e.g. ZoneInfo

[bolkedebruin]

then leave it for now, we can switch later

[Felix-neko]

Thank you for your PR, bro!
I've checked this version with #35483 DAG and the the problem with NameError: name 'timedelta' is not defined vanished.

[Taragolis]

@bolkedebruin Would you have a look again? Do you have any concern?

[potiuk]

LGTM

[bolkedebruin]

LGTM with one small question see above.

[Taragolis]

I've cherry picked changes into the #35798 and it fail in multiple new places, so I would suggest to close this one, and And continue working in that PR so we would sure that changes also would potentially work in pendulum 3

[Taragolis]

closed in favor of #35798