apt-pining: no priority (or zero) specified for pining

[berenger.morel@neutralite.org]

Well, the error message in title is not the exact one, but a 
translation of the one I have (which is exactly "W : Aucune priorité (ou 
zéro) n'a été spécifiée pour l'épinglage" but it is in french so...).

The consequence is that it seems my preferences is not used, testing 
packages have lower priority that unstable, which is not what I want.

My sources.list include a line for "wheezy main non-free", another for 
"unstable main" and the last for "experimental main" (my need was to add 
g++4.8, in the hope it include "std::set::emplace_hint(iterator, ...)").
Here is the sources.list:
=======================
deb http://ftp2.fr.debian.org/debian wheezy main non-free
deb http://ftp2.fr.debian.org/debian unstable main
deb http://ftp2.fr.debian.org/debian experimental main
=======================

My preferences file contain this:
=======================
Package: *
Pin: release a=wheezy
Pin-Priority: 900

Package: *
Pin: release a=unstable
Pin-Priority:200
=======================

I am quite sure the problem is obvious, but I did not play with 
preferences for ages... I'm simply trying to transform a computer for 
tinkering into a computer for real work, so I want to have only 
development stuff in experimental (C++11 is still not fully implemented 
by G++ and I want to use it. But I also want other stuff to be quiet in 
their changes.)

I have only one repo in sources.list.d and it worked before the add of 
unstable repo in both sources.list and preferences. Nothing is present 
in preferences.d/.

If someone knows how to solve that warning or have some clue about the 
error, I would be grateful.