[skeleton] drop whitelist_externals for flake8
whitelist_externals makes sense when used with sitepackages=true.
In this case it will always rely on $VIRTUAL_ENV/bin/flake8 so, the
whitelist_externals has no effect.
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/python-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python-cubicweb-documentation/html/*