(ONLY HAPPENS WITH LIBRARIANS)

What I expected to happen was...:
A librarian would sell me an enchanted book

What actually happened was...:
The librarian did not sell me an enchanted book, it would sometimes even want me to buy a bookshelf 

Steps to Reproduce:
1. Go into a new world

2. Get a villager spawn egg, lectern, and emeralds.

3. Make the villager get his job

4. Make sure he is wanting to sell a book 

5. Try to buy a book but it will not work