<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def sqlite_default():
    '''
    Prepend default scheme if none is specified. This helps provides backwards
    compatibility with old versions of taxtastic where sqlite was the automatic
    default database.
    '''
    def parse_url(url):
        # TODO: need separate option for a config file
        if url.endswith('.db') or url.endswith('.sqlite'):
            if not url.startswith('sqlite:///'):
                url = 'sqlite:///' + url
        elif url.endswith('.cfg') or url.endswith('.conf'):
            conf = configparser.SafeConfigParser(allow_no_value=True)
            conf.optionxform = str  # options are case-sensitive
            conf.read(url)
            url = conf.get('sqlalchemy', 'url')

        return url
    return parse_url