Did you try to install the proposed version, and in doing so, did you try to download and install the missing dependencies? If so, you have a broken system, and can only get it back if you purge all the 'missing dependencies' that you installed already. It might be quicker to completely re-install 15.04.
Did you try to install the proposed version, and in doing so, did you try to download and install the missing dependencies? If so, you have a broken system, and can only get it back if you purge all the 'missing dependencies' that you installed already. It might be quicker to completely re-install 15.04.