Skipping stage desktop/qt5 (already ran)
'application' has prerequisites that need to be staged: desktop/qt5
Skipping pull desktop/qt5 (already ran)
Skipping build desktop/qt5 (already ran)
Skipping stage desktop/qt5 (already ran)
Staging application 
Priming desktop/qt5 
'application' has prerequisites that need to be staged: desktop/qt5
Skipping pull desktop/qt5 (already ran)
Skipping build desktop/qt5 (already ran)
Skipping stage desktop/qt5 (already ran)
Priming application 
[Errno 21] Is a directory: '/home/liuxg/snappy/desktop/snappy-
playpen/snaptest/prime/snaptest'