pythonPackages.setuptools: specify priority

Both python3 and setuptools come with easy-install. For some magic
reason this hasn't caused any collisions yet, but it does with #17428.
We hereby prioritize the version that comes with setuptools.

Changed files
+1
pkgs
development
python-modules
setuptools
+1
pkgs/development/python-modules/setuptools/default.nix
···
homepage = http://pypi.python.org/pypi/setuptools;
license = with lib.licenses; [ psfl zpt20 ];
platforms = platforms.all;
};
}
···
homepage = http://pypi.python.org/pypi/setuptools;
license = with lib.licenses; [ psfl zpt20 ];
platforms = platforms.all;
+
priority = 10;
};
}