[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.

[bdist_wheel]
universal = 1

[check-manifest]
ignore =
  debian
  debian/*
  cubicweb.spec
  __pkginfo__.py