root@debian9:~# apt autoremove
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  grub-pc-bin
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
2 not fully installed or removed.
After this operation, 2,979 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 35306 files and directories currently installed.)
Removing grub-pc-bin (2.02~beta3-5+deb9u2) ...
Setting up linux-image-4.9.0-19-amd64 (4.9.320-2) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-4.9.0-19-amd64
/etc/kernel/postinst.d/zz-update-grub:
Searching for GRUB installation directory ... found: /boot/grub
/etc/default/grub: line 7: Debian: command not found
run-parts: /etc/kernel/postinst.d/zz-update-grub exited with return code 127
dpkg: error processing package linux-image-4.9.0-19-amd64 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of linux-image-amd64:
 linux-image-amd64 depends on linux-image-4.9.0-19-amd64; however:
  Package linux-image-4.9.0-19-amd64 is not configured yet.

dpkg: error processing package linux-image-amd64 (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 linux-image-4.9.0-19-amd64
 linux-image-amd64
E: Sub-process /usr/bin/dpkg returned an error code (1)