BRAINTREE, Mass. — The Roman Catholic Archdiocese of Boston is launching its most important fundraising drive of the year this weekend.The 2018 Catholic Appeal will be announced in the archdiocese's 286 parishes on Saturday and Sunday, and will be followed by commitment weekend on March 11 and 12.The appeal provides needed funding to the many ministries that serve the parishes, schools, community programs and other affiliated organizations and enables the Catholic community to carry the Gospel and assist those in need.