XCode alert says UPDATING_LOCKED_* on launch

Question

This is on OS X Yosemite. It appears when I try launching Xcode.

There are no updates shown in the App Store and there are no active downloading updates shown, either. Not exactly the pinnacle of Apple's great user experiences.

I hope I don't have to do a clean install…

Answer 1

This happened to me during the installation of iTunes 12.2.1 (1220C173).

I restarted my computer and ended the update, then Xcode opened properly.

Answer 2

Happened to me as well. Restarting the computer fixed it.