88 Let that solemn pronouncement of the Council of Trent be recalled to mind in which, under the stigma of anathema, it condemned these errors: "If anyone should say that on account of heresy or the hardships of cohabitation or a deliberate abuse of one party by the other the marriage tie may be loosened, let him be anathema;" and again: "If anyone should say that the Church errs in having taught or in teaching that, according to the teaching of the Gospel and the Apostles, the bond of marriage cannot be loosed because of the sin of adultery of either party; or that neither party, even though he be innocent, having given no cause for the sin of adultery, can contract another marriage during the lifetime of the other; and that he commits adultery who marries another after putting away his adulterous wife, and likewise that she commits adultery who puts away her husband and marries another: let him be anathemae."
Source: Casti Connubii (Vatican.va)