I was banging my head against this today so I figured I would share to hopefully reduce someone's banging their head time by a few minutes.
One of the things Bootstrap has done as part of their upgrade is to namespace their stuff, this is a good thing but is a bit of an arse if you weren't expecting something to be renamed.
Case in point, this used to work in Bootstrap 2.x
And this would return the popover element that is going to be created, as of Bootstrap 3 you have to write something like;
A simple change but one that (at the time of writing) wasn't documented anywhere that I could see.