As I noted a few days ago, the French law regarding annulment of marriage sounds very peculiar to Australian ears. This article gives some examples of what the courts there have found to be "an error about the person or the essential qualities of the person":
....marriages have been annulled for reasons such as impotence, if a partner does not reveal a previous marriage or a child, or if the wife hides the fact that she had been a prostitute.Very odd. These sort of factors are (apart from impotence) of a moral nature, and as such might be relevant to church law. But in a secular state, why not just let divorce deal with the issue of unhappiness with what might be called "inadequate disclosure" by the spouse, instead of pretending a valid marriage never took place?