Puppet could not retrieve information from plugin source

The reason this error comes up is you have pluginsync enabled, and you don't have any plugins to sync. pluginsync is enabled by default in the Ubuntu packages. Unfortunately, due to the design of puppet, the error message is a bit imposing, and throws up some pink in your otherwise green --test output.

There are two options:

1. Disable pluginsync on every client: edit /etc/puppet/puppet.conf and set pluginsync=false.

2. Create at least one plugin.

The easiest workaround is to create a single lib directory under a module of your choosing. Even an empty plugin is enough to cause the error to go away.

(Answer found in this bug report.)