I had to edit the location information on a photo taken recently with my iPhone. I use Photos app on the Mac & because such changes can be done in iPhoto, I naturally (and incorrectly) assumed I could also do it in Photos.
Nope, no can do. SO I exported the photo to the desktop, added it to iPhoto & made the required changes there. I then made sure to check the box "Include location info" while exporting it from iPhoto.
I then imported it to Photos and trashed the incorrect pic.
Thanks, Apple, for making things so easy.*
- Useless effing bastards.