Fix ubuntu variable replace

[andresriancho]

The whole story here: https://github.com/andresriancho/w3af/issues/10201

The main issue which is stopping me from building in ubuntu and then running in kali:

Hah, yes, this is inside the .deb file: Depends: python:any (>= 2.7.1-0ubuntu2), it seems that the ${python:Depends} from the control file is replaced (at build time) with the ubuntu specific package name