nox bug report (https://github.com/jonparrott/nox/issues/60)

check.py

import sys


def real_prefix():
    return getattr(sys, 'real_prefix', sys.prefix)


def main():
    # See: https://docs.python.org/3/library/platform.html#cross-platform
    if sys.maxsize == 2**63 - 1:
        print('Architecture: 64-bit')
    elif sys.maxsize == 2**31 - 1:
        print('Architecture: 32-bit')
    else:
        raise RuntimeError('Unexpected maxsize', sys.maxsize)

    print('      Prefix: {}'.format(sys.prefix))
    print(' Real prefix: {}'.format(real_prefix()))


if __name__ == '__main__':
    main()

nox.py

import sys

import nox


IS_MAC_OS_X = sys.platform == 'darwin'
# See: https://docs.python.org/3/library/platform.html#cross-platform
if sys.maxsize == 2**63 - 1:
    IS_64_BIT = True
elif sys.maxsize == 2**31 - 1:
    IS_64_BIT = False
else:
    raise RuntimeError('Unexpected maxsize', sys.maxsize)


@nox.session
@nox.parametrize('do_hack', [True, False])
def check(session, do_hack):
    session.interpreter = (
        '/Library/Frameworks/Python.framework/Versions/3.6/bin/python')

    cmd = ('python', 'check.py')
    if do_hack and IS_MAC_OS_X:
        if IS_64_BIT:
            cmd = ('arch', '-64') + cmd
        else:
            cmd = ('arch', '-32') + cmd

    session.run(*cmd)