Having the same issue of "Failed to copy file to the install data
folder. Failed to copy /Volumes/OS X Base System/Install macOS
Sierra.app/Contents/Resources/brtool to /OS X Install Data/brtool: The
file “brtool” couldn’t be opened because there is ...
Having the same issue of "Failed to copy file to the install data
folder. Failed to copy /Volumes/OS X Base System/Install macOS
Sierra.app/Contents/Resources/brtool to /OS X Install Data/brtool: The
file “brtool” couldn’t be opened because there is ...