I can second this. I hunted high and low for help on the XRandr and XKEYBOARD extension errors, which proved to be red herrings.
"cp lt.png library.png" fixed it for me.
I'm using calibre 3.7.0 on an up-to-date (but minimal) Ubuntu VM in Azure. I'm happy there was such a simple workaround.
Edit: Here's a related bug report on the Ubuntu package:
https://bugs.launchpad.net/ubuntu/+s...9?comments=all