Back to development: 4.2
Fix kupu zcml check.

For some reason you can do 'import Products.kupu' even when kupu is not in the eggs.
Using 'Products.kupu' still gives an error.
So we check for the existence of the Products.kupu.config module
to determine if we load our kupu.zcml.
Set our properties on install, also when kupu is not available.
Nuke trailing white space.
pyflakes