Running KF5/Plasma 5 from current git + Qt 5.4.1.

When the executable of a *.desktop file can't be found within $PATH, the resulting error message is misleading and not userfriendly.
Applications like krunner, Dolphin, Plasma etc. will just show the raw error message which is a bit of a UX issue.

e.g here 'skype' is located in /opt/bin/skype, but until I added it /opt/bin/ wasn't part of my $PATH.
When trying to launch 'Skype' via its *.desktop file through krunner, kickoff etc. just resulted in a error dialog showing:

KDEInit could not launch 'skype':
Could not open library '/usr/lib64/libkdeinit5_skype'.
Cannot load library /usr/lib64/libkdeinit5_skype: (/usr/lib64/libkdeinit5_skype.so: cannot open shared object file: No such file or directory)

IMHO there are 2 things to be done here:
- when a *.desktop file with Type=Application is launched, kdeinit shouldn't try to load a library
- the error handling between kdeinit's clients and kdeinit itself should be improved to generate more meaningful error messages (e.g. "The application 'skype' could not be located and executed. Please check your $PATH variable.").

As I'm missing sufficient knowledge of kinit's internal workings, I might be wrong with some of the points above. Just wanted to outline the experience from a user's POV.