This is more an aide-memoire for me as I just had this error. But I thought that sharing it as a blog post would be handy just in case anyone else gets the issue.
So what happened?
My laptop just errored on boot.
The first error prevented the laptop booting and referred to a missing kernel.
The second error referred to
Error: environment block too small Press any key to continue...
Ubuntu 18.04.2 x86_64
So after a little Googling I found the cause of the issue. It seems that if the
grubenv file is greater that 1024 bytes then the error will occurr. Typically this is caused by manually editing the file, but I have not done this so I guess an update has caused this issue.
Warning: we are messing around with config files which may render your computer non bootable. Ensure you have backups, or a care free attitude to life. Do not try and blame me for data loss. You typed the commands in, not me!
Then I opened a terminal and did the following.
Delete the grubenv
sudo rm /boot/grub/grubenv
Create a new grubenv
sudo grub-editenv /boot/grub/grubenv create
I then rebooted and the error was gone :)