[debian] Let dh-python generate dependencies from requires.txt

We add a pydist-overrides to handle cubicweb, as it's not available in official Debian repositories.

debian/control

@@ -14,7 +14,6 @@ X-Python-Version: >= 2.7
 Package: cubicweb-postgis
 Architecture: all
 Depends:
- python-cubicweb (>= 3.24.0),
  ${python:Depends},
  ${misc:Depends},
 Description: Cube for GIS data support using PostGIS

debian/pydist-overrides

+cubicweb python-cubicweb