In MacOS X 1010.5 you need iPhoto version 9.6.1.
This update used to be available from the App Store by reinstalling iPhoto from the Purchases history. But Apple stopped selling iPhoto from the App Store, and right now it looks like iPhoto had been removed completely from the App Store.
if you do not see iPhoto in your Purchase History. I do not know of any way to update the incompatible iPhoto other than sweet talking the AppStore support into providing an installer for you. An auto-update to a system that renders your iPhoto useless should not be possible.
This used to work until yesterday: Perhaps the AppStore in your country has still the update. Hurry and try it.
Barney-15E's user tip explains how to update to iPhoto 9.6.1 by reinstalling your App Store purchase.
See this link: Get iPhoto 9.6.1 if you didn't update before OS X 10.10.3
Basically, move the incompatible iPhoto version from the Applications folder to the Trash (the application, not your iPhoto Library). Then sign into the AppStore and open the Purchases tab. It should now show "Install" to the right of iPhoto.