Puppet "solved" this problem by using a shorter default temp directory path for puppet-install. See: https://tickets.puppetlabs.com/browse/PUP-4854 and puppetlabs/puppet#4090 Since librarian-puppet sets its own temp directory though that fix has no effect in this case.
While trying to use librarian-puppet to install a module on Windows, I got the following error:
I believe this is occuring because of the maximum path length of 260 characters in the Windows API, as the path cited in the error message is 262 characters long.
Puppet "solved" this problem by using a shorter default temp directory path for puppet-install. See: https://tickets.puppetlabs.com/browse/PUP-4854 and puppetlabs/puppet#4090 Since librarian-puppet sets its own temp directory though that fix has no effect in this case.