python-astral fails to build with Python 3.9.0b1.

=================================== FAILURES ===================================
______________________________ test_AllLocations _______________________________

observer = Observer(latitude=64.16666666666667, longitude=-51.583333333333336, elevation=0.0)
date = datetime.date(2020, 5, 21), depression = <Depression.CIVIL: 6.0>
tzinfo = <UTC>

    def dawn(
        observer: Observer,
        date: Optional[datetime.date] = None,
        depression: Union[float, Depression] = Depression.CIVIL,
        tzinfo: datetime.tzinfo = pytz.utc,
    ) -> datetime.datetime:
        """Calculate dawn time.
    
        Args:
            observer:   Observer to calculate dawn for
            date:       Date to calculate for. Default is today's date in the timezone `tzinfo`.
            depression: Number of degrees below the horizon to use to calculate dawn.
                        Default is for Civil dawn i.e. 6.0
            tzinfo:     Timezone to return times in. Default is UTC.
    
        Returns:
            Date and time at which dawn occurs.
    
        Raises:
            ValueError: if dawn does not occur on the specified date
        """
        if date is None:
            date = today(tzinfo)
    
        dep: float = 0.0
        if isinstance(depression, Depression):
            dep = depression.value
        else:
            dep = depression
    
        try:
>           return time_of_transit(
                observer, date, 90.0 + dep, SunDirection.RISING
            ).astimezone(tzinfo)

../../BUILDROOT/python-astral-2.1-1.fc33.x86_64/usr/lib/python3.9/site-packages/astral/sun.py:734: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

observer = Observer(latitude=64.16666666666667, longitude=-51.583333333333336, elevation=0.0)
date = datetime.date(2020, 5, 21), zenith = 96.0
direction = <SunDirection.RISING: 1>

    def time_of_transit(
        observer: Observer, date: datetime.date, zenith: float, direction: SunDirection
    ) -> datetime.datetime:
        """Calculate the time in the UTC timezone when the sun transits the specificed zenith
    
        Args:
            observer: An observer viewing the sun at a specific, latitude, longitude and elevation
            date: The date to calculate for
            zenith: The zenith angle for which to calculate the transit time
            direction: The direction that the sun is traversing
    
        Returns:
            the time when the sun transits the specificed zenith
        """
        if observer.latitude > 89.8:
            latitude = 89.8
        elif observer.latitude < -89.8:
            latitude = -89.8
        else:
            latitude = observer.latitude
    
        adjustment_for_elevation = 0.0
        if isinstance(observer.elevation, float) and observer.elevation > 0.0:
            adjustment_for_elevation = adjust_to_horizon(observer.elevation)
        elif isinstance(observer.elevation, tuple):
            adjustment_for_elevation = adjust_to_obscuring_feature(observer.elevation)
    
        adjustment_for_refraction = refraction_at_zenith(zenith + adjustment_for_elevation)
    
        jd = julianday(date)
        t = jday_to_jcentury(jd)
        solarDec = sun_declination(t)
    
>       hourangle = hour_angle(
            latitude,
            solarDec,
            zenith + adjustment_for_elevation - adjustment_for_refraction,
            direction,
        )

../../BUILDROOT/python-astral-2.1-1.fc33.x86_64/usr/lib/python3.9/site-packages/astral/sun.py:355: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

latitude = 64.16666666666667, declination = 20.23388643880472
zenith = 95.9450968313411, direction = <SunDirection.RISING: 1>

    def hour_angle(
        latitude: float, declination: float, zenith: float, direction: SunDirection
    ) -> float:
        """Calculate the hour angle of the sun
    
        See https://en.wikipedia.org/wiki/Hour_angle#Solar_hour_angle
    
        Args:
            latitude: The latitude of the obersver
            declination: The declination of the sun
            zenith: The zenith angle of the sun
            direction: The direction of traversal of the sun
    
        Raises:
            ValueError
        """
    
        latitude_rad = radians(latitude)
        declination_rad = radians(declination)
        zenith_rad = radians(zenith)
    
        # n = cos(zenith_rad)
        # d = cos(latitude_rad) * cos(declination_rad)
        # t = tan(latitude_rad) * tan(declination_rad)
        # h = (n / d) - t
    
        h = (cos(zenith_rad) - sin(latitude_rad) * sin(declination_rad)) / (
            cos(latitude_rad) * cos(declination_rad)
        )
    
>       HA = acos(h)
E       ValueError: math domain error

../../BUILDROOT/python-astral-2.1-1.fc33.x86_64/usr/lib/python3.9/site-packages/astral/sun.py:253: ValueError

The above exception was the direct cause of the following exception:

test_database = {'africa': {'abuja': [LocationInfo(name='Abuja', region='Nigeria', timezone='Africa/Lagos', latitude=9.083333333333334..., region='Faroe Islands', timezone='Atlantic/Faroe', latitude=62.083333333333336, longitude=-6.933333333333334)]}, ...}

    def test_AllLocations(test_database):
        for location in all_locations(test_database):
>           sun(location.observer)

src/test/test_all.py:6: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../BUILDROOT/python-astral-2.1-1.fc33.x86_64/usr/lib/python3.9/site-packages/astral/sun.py:1120: in sun
    "dawn": dawn(observer, date, dawn_dusk_depression, tzinfo),
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

observer = Observer(latitude=64.16666666666667, longitude=-51.583333333333336, elevation=0.0)
date = datetime.date(2020, 5, 21), depression = <Depression.CIVIL: 6.0>
tzinfo = <UTC>

    def dawn(
        observer: Observer,
        date: Optional[datetime.date] = None,
        depression: Union[float, Depression] = Depression.CIVIL,
        tzinfo: datetime.tzinfo = pytz.utc,
    ) -> datetime.datetime:
        """Calculate dawn time.
    
        Args:
            observer:   Observer to calculate dawn for
            date:       Date to calculate for. Default is today's date in the timezone `tzinfo`.
            depression: Number of degrees below the horizon to use to calculate dawn.
                        Default is for Civil dawn i.e. 6.0
            tzinfo:     Timezone to return times in. Default is UTC.
    
        Returns:
            Date and time at which dawn occurs.
    
        Raises:
            ValueError: if dawn does not occur on the specified date
        """
        if date is None:
            date = today(tzinfo)
    
        dep: float = 0.0
        if isinstance(depression, Depression):
            dep = depression.value
        else:
            dep = depression
    
        try:
            return time_of_transit(
                observer, date, 90.0 + dep, SunDirection.RISING
            ).astimezone(tzinfo)
        except ValueError as exc:
            if exc.args[0] == "math domain error":
>               raise ValueError(
                    f"Sun never reaches {dep} degrees below the horizon, at this location."
                ) from exc
E               ValueError: Sun never reaches 6.0 degrees below the horizon, at this location.

../../BUILDROOT/python-astral-2.1-1.fc33.x86_64/usr/lib/python3.9/site-packages/astral/sun.py:739: ValueError
===================== 1 failed, 264 passed in 1.38 seconds =====================

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01396551-python-astral/

For all our attempts to build python-astral with Python 3.9, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/package/python-astral/

Testing and mass rebuild of packages is happening in copr. You can follow these instructions to test locally in mock if your package builds with Python 3.9:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/

Let us know here if you have any questions.

Python 3.9 will be included in Fedora 33. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.9.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires), so if this package is required a lot, it's important for us to get it fixed soon.
We'd appreciate help from the people who know this package best, but if you don't want to work on this now, let us know so we can try to work around it on our side.