As we deprecated 'all' we can just as well rely on only one project
given (which is also what we do in gocd) to ease error reporting.
The old method of running all projects in a loop stemed from the
old pkglistgen not having a scheduler so we relied on serial execution.
For some reason, valid yaml is not supported - the indentation required
is rather wild. But to check the syntax before commit, you can use the
plugin locally:
1870e989a4