iPhoto requesting Aperture upgrade.

I recently attempted to use Photos and selected my iPhoto library during setup. Photos could not open the library. Now, when I try to open the library with iPhoto, it says "Aperture library needs to be upgraded." and further explains that to open this Aperture library in iPhoto, I need Aperture 3.3 or later. I have never had Aperture on my system, but I clicked the Update Aperture button. It took me to the App Store, which helpfully informed me that what I was looking for was no longer available. I have attempted to access the Repair Library dialogue, but iPhoto immediately displays the same error message and will go no further. Any idea on how to repair my iPhoto library would be appreciated. Thanks.