No contract shall be made by the city council of a city of the second class or village board of trustees or any committee or member of such city council or village board of trustees, and no expense shall be incurred by any of the officers or departments of the municipality, whether the object of the expenditures shall have been ordered by the city council or village board of trustees or not, unless an appropriation shall have been previously made concerning such expense, except as otherwise expressly provided in section 17-708.