I do not think that this view about the absolute exceptionless prohibition of divorce is correct.
In Matthew 12, Jesus holds David guiltless even when he breaks a rule from God (the showbread rule is clearly described in the Old Testament as being from God):
He answered, "Haven't you read what David did when he and his companions were hungry? 4He entered the house of God, and he and his companions ate the consecrated bread—which was not lawful for them to do, but only for the priests.
Later in the same chapter, Jesus basically states, despite what God's own law states, work on the Sabbath can be justified in certain circumstances.
He said to them, "If any of you has a sheep and it falls into a pit on the Sabbath, will you not take hold of it and lift it out? 12How much more valuable is a man than a sheep! Therefore it is lawful to do good on the Sabbath."
The law concerning working on the Sabbath is not "man's law", it comes from God:
Moses assembled the whole Israelite community and said to them, "These are the things the LORD has commanded you to do: 2 For six days, work is to be done, but the seventh day shall be your holy day, a Sabbath of rest to the LORD. Whoever does any work on it must be put to death.
People try to preserve the notion that God's laws are "exceptionless" by claiming that pulling a sheep out of a pit is not "work". It sure seems like work to me. Either way, there is the very strong implication that Jesus would have approved of doctors performing emergency surgery on the Sabbath - it is lawful to do good on the Sabbath. And performing surgery is certainly work. So things are not as cut and dried as some would have you believe.
And we also have the example of David. Jesus condones his actions even though God's own law forbad anyone but the priests from eating the showbread.
The obvious conclusion: The prohibition against divorce should not be seen by us as an "exceptionless" rule. Jesus gives us multiple examples of times when it can be justifiable to break even the laws that come from God's own mouth.