gdm3 package blocking while updating

Hi,

I just tried to install 17.10 with the regular ubuntu desktop image, and ran into the problem that the desktop freezes right after entering the password at login (see #1726842 ).

I then went into the recovery root session at the console and did an apt-get upgrade, which pulled in a new gdm3 package. However, installation of the package was hanging, since it tried to restart gdm3 (after issuing some error message that it can't detect the running state). I had to abort with Ctrl-C.

A package should never block the installation procedure, especially not in recovery mode.