This bug was fixed in the package grub2-signed - 1.102
--------------- grub2-signed (1.102) cosmic; urgency=medium
* Call grub-check-signatures before calling grub-install, not after, to avoid overwriting the boot loader on disk with one that will fail to load. LP: #1786491.
-- Steve Langasek <email address hidden> Fri, 10 Aug 2018 12:28:40 -0700
This bug was fixed in the package grub2-signed - 1.102
---------------
grub2-signed (1.102) cosmic; urgency=medium
* Call grub-check- signatures before calling grub-install, not after, to
avoid overwriting the boot loader on disk with one that will fail to
load. LP: #1786491.
-- Steve Langasek <email address hidden> Fri, 10 Aug 2018 12:28:40 -0700