"John D MacDonald" and "Marie J Mitchell (Desdouets)" were married in Boston in 1927, according to a Massachusetts marriage index. John's name is transcribed incorrectly as Colin D MacDonald (Colin is the middle name of the John MacDonald listed above him.) The source for their marriage info is given as Vol. 2, page 88.
FamilySearch.org DOES have Boston 1927 Marriage License records online here:
https://www.familysearch.org/records/images/beta/search-results?place=4229284&startDate=1927-01-01&endDate=1927-12-31&lifeEvent=102860&lifeEventRecordTypes=104727&page=1&pageSize=100However, I don't see an INDEX. Presumably their license is here but you would need to go through 10,000 pages to find it!

I'm just including this in case you find a reference to their certificate number elsewhere.