If you are in the process of migrating your CM07 environment to CM12 and you are using already an App-V integrated solution , be sure that you have upgrade your App-V client to the correct version ! The correct supported version is App-V 4.6 SP1 cu5 .
If the Existing CM07 client has the App-V client 4.6 or 4.6 SP1 installed , client migration will FAIL as shown below in the log file !! The only correct supported version is App-V 4.6 SP1 cu5 !
Hope it Helps ,
Kenny Buntinx