izpack2app runtime error

From Reiner Kromer:

today I tried out the izpack2app Python script. Unfortunately there was a
recurring error everytime I executed it:

rk@gogh:~/pjs/ianus/ianus-client-install$ python
IzPack/utils/izpack2app/izpack2app.py dist/ianus-client-install_2.0.2.jar
dist/ianus-client-install_2.0.2.app
Traceback (most recent call last):
File "IzPack/utils/izpack2app/izpack2app.py", line 52, in <module>
main()
File "IzPack/utils/izpack2app/izpack2app.py", line 34, in main
os.mkdir(java_folder)
OSError: [Errno 17] File exists:
'dist/ianus-client-install_2.0.2.app/Contents/Resources/Java/'

Now I have found out that izpack2app tries to create a directory
"java_folder" which contains "Contents/Resources/Java/" at the end. But this
directory is also included in the Mac-App-Template which is copied
recursively before.