numpy fails to build with Python 3.9.0a3.

________________________ TestMatmul.test_matmul_object _________________________
self = <numpy.core.tests.test_multiarray.TestMatmul object at 0x7ff9bc008ca0>
    def test_matmul_object(self):
        import fractions
    
        f = np.vectorize(fractions.Fraction)
        def random_ints():
            return np.random.randint(1, 1000, size=(10, 3, 3))
>       M1 = f(random_ints(), random_ints())
f          = <numpy.vectorize object at 0x7ff9bc6751f0>
fractions  = <module 'fractions' from '/usr/lib64/python3.9/fractions.py'>
random_ints = <function TestMatmul.test_matmul_object.<locals>.random_ints at 0x7ff9bcc2d700>
self       = <numpy.core.tests.test_multiarray.TestMatmul object at 0x7ff9bc008ca0>
numpy/core/tests/test_multiarray.py:6259: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
numpy/lib/function_base.py:2091: in __call__
    return self._vectorize_call(func=func, args=vargs)
numpy/lib/function_base.py:2161: in _vectorize_call
    ufunc, otypes = self._get_ufunc_and_otypes(func=func, args=args)
numpy/lib/function_base.py:2121: in _get_ufunc_and_otypes
    outputs = func(*inputs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
cls = <class 'fractions.Fraction'>, numerator = 483, denominator = 809
    def __new__(cls, numerator=0, denominator=None, *, _normalize=True):
        """Constructs a Rational.
    
        Takes a string like '3/2' or '1.5', another Rational instance, a
        numerator/denominator pair, or a float.
    
        Examples
        --------
    
        >>> Fraction(10, -8)
        Fraction(-5, 4)
        >>> Fraction(Fraction(1, 7), 5)
        Fraction(1, 35)
        >>> Fraction(Fraction(1, 7), Fraction(2, 3))
        Fraction(3, 14)
        >>> Fraction('314')
        Fraction(314, 1)
        >>> Fraction('-35/4')
        Fraction(-35, 4)
        >>> Fraction('3.1415') # conversion from numeric string
        Fraction(6283, 2000)
        >>> Fraction('-47e-2') # string may include a decimal exponent
        Fraction(-47, 100)
        >>> Fraction(1.47)  # direct construction from float (exact conversion)
        Fraction(6620291452234629, 4503599627370496)
        >>> Fraction(2.25)
        Fraction(9, 4)
        >>> Fraction(Decimal('1.47'))
        Fraction(147, 100)
    
        """
        self = super(Fraction, cls).__new__(cls)
    
        if denominator is None:
            if type(numerator) is int:
                self._numerator = numerator
                self._denominator = 1
                return self
    
            elif isinstance(numerator, numbers.Rational):
                self._numerator = numerator.numerator
                self._denominator = numerator.denominator
                return self
    
            elif isinstance(numerator, (float, Decimal)):
                # Exact conversion
                self._numerator, self._denominator = numerator.as_integer_ratio()
                return self
    
            elif isinstance(numerator, str):
                # Handle construction from strings.
                m = _RATIONAL_FORMAT.match(numerator)
                if m is None:
                    raise ValueError('Invalid literal for Fraction: %r' %
                                     numerator)
                numerator = int(m.group('num') or '0')
                denom = m.group('denom')
                if denom:
                    denominator = int(denom)
                else:
                    denominator = 1
                    decimal = m.group('decimal')
                    if decimal:
                        scale = 10**len(decimal)
                        numerator = numerator * scale + int(decimal)
                        denominator *= scale
                    exp = m.group('exp')
                    if exp:
                        exp = int(exp)
                        if exp >= 0:
                            numerator *= 10**exp
                        else:
                            denominator *= 10**-exp
                if m.group('sign') == '-':
                    numerator = -numerator
    
            else:
                raise TypeError("argument should be a string "
                                "or a Rational instance")
    
        elif type(numerator) is int is type(denominator):
            pass # *very* normal case
    
        elif (isinstance(numerator, numbers.Rational) and
            isinstance(denominator, numbers.Rational)):
            numerator, denominator = (
                numerator.numerator * denominator.denominator,
                denominator.numerator * numerator.denominator
                )
        else:
            raise TypeError("both arguments should be "
                            "Rational instances")
    
        if denominator == 0:
            raise ZeroDivisionError('Fraction(%s, 0)' % numerator)
        if _normalize:
            if type(numerator) is int is type(denominator):
                # *very* normal case
                g = math.gcd(numerator, denominator)
                if denominator < 0:
                    g = -g
            else:
>               g = _gcd(numerator, denominator)
E               NameError: name '_gcd' is not defined
__class__  = <class 'fractions.Fraction'>
_normalize = True
cls        = <class 'fractions.Fraction'>
denominator = 809
numerator  = 483
self       = <[AttributeError("_numerator") raised in repr()] Fraction object at 0x7ff9bc6753a0>
/usr/lib64/python3.9/fractions.py:164: NameError


See https://docs.python.org/3.9/whatsnew/3.9.html#removed

"fractions.gcd() function has been removed, it was deprecated since Python 3.5 (bpo-22486): use math.gcd() instead."


For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01208199-numpy/

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

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.