Lightroom doesn't currently support importing from the Apple Photos' Library.
You may import the images manually but the edit won't be available in Lightroom.
You may consider to export the images with the edits and then import them to Lightroom.
If I cannot import photos from 'Photos' in Apple why have you a version of Adobe Lightroom 6 made for Apple Mac. This to me looks like false advertising if you cannot import photos and manipulate them in Apple Mac's. Have I spent $186.00 for a programme that does not work on my equipment.
I am sorry for the inconvenience caused to you.
However, Photos is an application which is provided by Apple.
On the other hand, Lightroom 6 is a 3rd party application which can be used on Mac computers and also works fine on Mac computers.
There is no integration of Photos application like Aperture and iPhotos as of now.
I would request you to provide us with a feature request.
Feature Request/Bug Report Form
Some more info at this thread.
It is not the 'fault' of Lightroom! It is Apple's insistence of hiding photos- blame Apple!