import operator


def _ensure_int(x, name='unknown', must_be='an int'):
    """Ensure a variable is an integer."""
    # This is preferred over numbers.Integral, see:
    # https://github.com/scipy/scipy/pull/7351#issuecomment-299713159
    try:
        x = int(operator.index(x))
    except TypeError:
        raise TypeError('%s must be %s, got %s' % (name, must_be, type(x)))
    return x