The second definition of "pity": something to be regretted <it's a pity you can't go> (Dictionary and Thesaurus - Merriam-Webster Online)
From their English Learner's dictionary:
2 [singular] : something that causes sadness or disappointment
▪ It's a pity [=shame] you can't go. = Pity (that) you can't go. [=I'm sorry that you can't go] ▪ I'll be out of town on that day—a (great) pity, since I'd love to see you. ▪ He didn't live to see his daughter grow up, and that's a pity.
Student or Learner