1. Whenever the governing body of any municipality within this state has made any contract for any project provided herein or shall hereafter make any assessment against any tract within any improvement district for any purpose authorized herein, and has in making such contract or assessment acted in good faith and without fraud, or shall hereafter act in good faith and without fraud, the contract and assessment shall be valid and enforceable as such, and the assessment shall be a lien upon the tract upon which the same purports to be a lien.
2. It shall be no objection to the validity of such contract, assessment or lien that:
(a) The contract for such project was not awarded in the manner or at the time required hereby, or otherwise.
(b) The assessment was made by an unauthorized officer or person, if the same shall have been confirmed by the authorities of the municipality.
(c) The assessment is based upon an improper basis of benefits to the tract within such improvement district, unless it shall be made to appear that the municipal authorities acted fraudulently or oppressively in making such assessment.