anchor.diff:   *  External libraries
    */
   assert flite != null -> alsa-lib != null;
  -assert libxcbshmExtlib -> xorg.libxcb != null;
  -assert libxcbxfixesExtlib -> xorg.libxcb != null;
  -assert libxcbshapeExtlib -> xorg.libxcb != null;
  +assert libxcbshmExtlib -> libxcb != null;
  +assert libxcbxfixesExtlib -> libxcb != null;
  +assert libxcbshapeExtlib -> libxcb != null;
   assert gnutls != null -> openssl == null;
   assert openssl != null -> gnutls == null;
   
  
positive.code:     x264
      x265
      xavs
      xorg.libX11
      xorg.libxcb
      xorg.libXext
      xorg.libXfixes
      xorg.libXv
      #xorg.libXvMC
      xorg.xproto
      xvidcore
      xz
      zeromq4
  
negative.code: , x264
  , x265
  , xavs
  , xproto
  , xvidcore
  , xz
  , zeromq4
  