Comment 1 for bug 1823061

OK I found the solution at https://unix.stackexchange.com/questions/202332/sudo-source-command-not-found/202334 but it gave another problem:

$ sudo -s source vars
You appear to be sourcing an Easy-RSA 'vars' file.
This is no longer necessary and is disallowed. See the section called
'How to use this file' near the top comments for more details.