Click on the Finder (smiley face) in the dock (bar at the bottom of the screen)
Click on Go (at the top of the screen)
Click on Go to folder (bottom of the list)
Copy and paste the following: ~/Library/Pictures
Click Go
Once in this location click on 'iPhoto Library' once
Click 'Edit' (top of the screen)
Click 'Copy'
Click 'Desktop' on the left side of the Finder window
Click 'Edit' (top of the screen)
Click 'Paste item'
You have now got a backup of all your photos on the mac (if stored in iPhoto)
Now open the 'Photos' application (from the dock or from the spotlight search at the top right of the screen)
It should prompt you to migrate a library
Click 'iPhoto Library'
This now imports all of your photos into the replacement program Photos (iPhoto no longer works past 10.10.4)
Resolved?