Be careful not to bad mouth your old boss! It's okay to share some qualities that might have affected you or the staff negatively. Keep your response positive. In talking about other people's flaws, share what you learned or how you learned to work with them. Sometimes the downfalls of your coworkers can be opportunities for you to share your skills. See if you can flip this question around to show off how well you handled a difficult personality.
"The pharmacist wasn't very personable. They were professional, but just not much of a people person. I love working with people, so I took it as an opportunity to shine when I worked with customers, making sure they received the best service."
"I have worked for challenging Pharmacists. I value my professional work relationships and Sometimes we agreed to disagree and that's ok."