Each member of Council, the Mayor, the City Clerk and each director or chief of a City office, department or agency, including the Judge of the Municipal Court and the City Attorney, shall, before entering upon his duties, take and subscribe to the following oath or affirmation, to be filed and kept in the office of the City Clerk: "I solemnly swear (or affirm) that I will support the Constitution of the United States of America and the Constitution of the State of West Virginia, and that I will faithfully discharge the duties of to the best of my skill and judgment". When an officer or employee of the City shall have filed such oath, together with the certificate of the officer administering it, with the City Clerk and shall have given bond as required by law, he shall be considered as having qualified for the position to which he was elected or appointed; provided, however, that if any person so elected or appointed shall not qualify in the manner herein prescribed within 20 days after he shall have been officially declared elected or appointed thereto, said position shall by reason thereof become vacant.