Section 11.4.  Contest of assessment.
   No suit or action of any kind shall be instituted or maintained for the purpose of  contesting or enjoining the collection of any special assessment or reassessment (a) unless, within 30 days after the confirmation of the special assessment roll, written notice is given to the city clerk for attention of the council indicating an intention to file such suit or action and stating the grounds on which it is claimed such assessment is illegal and (b) unless such suit or action shall be commenced within sixty (60) days after the confirmation of the roll.  If the city attorney submits a written opinion finding said roll illegal, in whole or in part, the council may revoke its confirmation, correct the illegality if possible and reconfirm the same, provided that no property which is not involved in the illegality shall be assessed more than was imposed upon the original confirmation without further notice and hearing thereon.