Running "make" fails

As of 2e2add8d11bc7c11bf950ad0b2f015e5d4a048dc:
```
[quickwkt(master)] make
pyrcc4 -o resources.py  resources.qrc
Cannot find file: quickwkt_icon.png
Cannot find file: about_icon.png
Cannot find file: paypal_icon.png
No resources in resource description.
Makefile:17: recipe for target 'resources.py' failed
make: *** [resources.py] Error 1
```