def _set_sql_mode(sql_mode, dbapi_con, connection_rec):
    """Set the sql_mode session variable.

    MySQL supports several server modes. The default is None, but sessions
    may choose to enable server modes like TRADITIONAL, ANSI,
    several STRICT_* modes and others.

    Note: passing in '' (empty string) for sql_mode clears
    the SQL mode for the session, overriding a potentially set
    server default.
    """
    cursor = dbapi_con.cursor()
    cursor.execute('SET SESSION sql_mode = %s', [sql_mode])
