My iMac is running current OS/X Yosemite 10.11.3. It's a big development machine, not rebooted for some weeks. It has many apps from the Mac app store, among them
Clocks. Suddenly (it worked yesterday)
TextWrangler wouldn't launch. The listing from
2016/02/16 11:12:38.116 com.apple.xpc.launchd: (com.barebones.textwrangler.64672) Service exited with abnormal code: 173
and it wouldn't do anything else until I threw it in the trash and re-downloaded it from the app store. Then I noticed
Clocks wasn't running (it, too, worked yesterday). It gave the same error code 173 and was fixed by re-downloading.
I see from Why do App Store applications transferred into ~/Applications on another machine not launch? that error 173 is caused by the app receipt being invalid.
Is there some reason why receipts for some of my apps from the store would suddenly become invalid?