Bug #86407
Updated by Oliver Hader over 5 years ago
In composer mode several directories are arranged outside the public root-path. When trying to copy to those folders, the public root-path is prefixed due an invalid check which is too strict. The expectation is to use public root-path (PATH_site) when resolving relative paths here.
see https://github.com/FriendsOfTYPO3/introduction/issues/13
introduced in https://review.typo3.org/#/c/57241/