Is an expiatory oath (kaffarat yamin) obligatory upon someone who swore not to go to a city, but then went there for fear of displeasing his parents?

You are required to offer expiation for breaking an oath (kaffarat yamin), and you have done well in pleasing your parents, as the Prophet, peace and blessings be upon him, said: "Whoever takes an oath and then sees something better than it, let him do what is better and offer expiation for his oath." The expiation for an oath is feeding ten poor persons, or clothing them, or freeing a slave. If one cannot find any of these, then he should fast for three days, as Allah the Almighty says: (Its expiation is the feeding of ten poor persons from the average of what you feed your [own] families or clothing them or freeing a slave. But whoever finds not [the means to do so] - then a fast of three days). It is not permissible to pay its value in cash according to the majority of scholars.