Return a MSSQL connection.

def _get_conn(ret=None):
    '''
    Return a MSSQL connection.
    '''
    _options = _get_options(ret)
    dsn = _options.get('dsn')
    user = _options.get('user')
    passwd = _options.get('passwd')

    return pyodbc.connect('DSN={0};UID={1};PWD={2}'.format(
            dsn,
            user,
            passwd))