Every officer, elected or appointed, before entering upon the duties of his office, shall take the constitutional oath of office and shall file the same with the clerk, together with any bond required by law or by the council. In the case of failure to comply with the provisions of this section within ten days from the date of his election or appointment, such officer shall be deemed to have declined the office and such office shall thereupon be vacant, unless the council shall, by resolution, extend the time in which such officer may qualify as above set forth.