Mayor Marty Walsh announced the city’s suit, challenging the commission’s awarding of the sole Boston-area casino license to a Wynn Resorts project in Everett, at a Monday afternoon press conference. Walsh feuded with the commission throughout 2014, as he argued Boston should be considered a host community for the Wynn proposal – and for the proposed Mohegan Sun project in Revere that lost out on the casino license to Wynn – but was rebuffed by the gaming commission in that effort.