[...]
Preparing to build qt5conf 
Building qt5conf 
make -j4
make: Nothing to be done for 'all'.
make install DESTDIR=/tmp/snappy-playpen/notes/parts/qt5conf/install
install -D -m644 snappy-qt5.conf /tmp/snappy-playpen/notes/parts/qt5conf/install/etc/xdg/qtchooser
Staging notes 
Staging qt5conf 
[Errno 21] És un directori: '/tmp/snappy-
playpen/notes/stage/etc/xdg/qtchooser'

(which translates to "It's a directory")