I'm also affected here: I'm trying to update to Mesa 17.3 after
installing the 390.48.2~bpo9+3 drivers on my Stretch laptop (I'm using a
hybrid graphics laptop so I need both drivers for my setup), but either
I get updated Mesa or lose the nVidia blob due to conflicts with the new
packaging specs (??), rendering my setup completely unupgradable and
unusable.