make RELEASE (here: kernel): template.ucl: line: 33, column: 0 - 'key must begin with a letter', character: '.'

Building the OS for jails via the RELEASE infrastructure,
this doesn't work anymore since a couple of days for now with 15-STABLE as well as with recent
CURRENT;


 [...]

--- create-packages-kernel ---
/pool/sources/CURRENT/src/release/packages/generate-ucl.lua: fail to
parse(/pool/sources/CURRENT/src/release/packages/template.ucl): error while parsing
/pool/sources/CURRENT/src/release/packages/template.ucl: line: 33, column: 0 - 'key must begin
with a letter', character: '.' *** [create-kernel-packages-extra-flavor-default-GENERIC] Error
code 1

-- 

A FreeBSD user