Replaces NoneType with ''

    >>> none_to_blank(None, '')
    ''
    >>> none_to_blank(None)
    ''
    >>> none_to_blank('something', '')
    u'something'
    >>> none_to_blank(['1', None])
    [u'1', '']

    :param s: String to replace
    :para exchange: Character to return for None, default is blank ('')
    :return: If s is None, returns exchange

def none_to_blank(s, exchange=''):
    """Replaces NoneType with ''

    >>> none_to_blank(None, '')
    ''
    >>> none_to_blank(None)
    ''
    >>> none_to_blank('something', '')
    u'something'
    >>> none_to_blank(['1', None])
    [u'1', '']

    :param s: String to replace
    :para exchange: Character to return for None, default is blank ('')
    :return: If s is None, returns exchange
    """
    if isinstance(s, list):
        return [none_to_blank(z) for y, z in enumerate(s)]
    return exchange if s is None else unicode(s)