the polygon to lines conversion works by using v.to.lines tool from grass.
Depending how qgis is installed and the os, GRASS might not be availble, we should do a check and suggest the user some possible solutions. I.e. on mac osx it happended that it was installed but the PATHs were not set properly:
see https://www.reddit.com/r/QGIS/comments/1q7emaa/why_doesnt_grass_show_in_qgis_how_to_fix_it/ and this solution:
export GRASS_PREFIX=/opt/local/lib/grass84
export PATH=$GRASS_PREFIX/bin:$PATH
open /Applications/QGIS.app
the polygon to lines conversion works by using v.to.lines tool from grass.
Depending how qgis is installed and the os, GRASS might not be availble, we should do a check and suggest the user some possible solutions. I.e. on mac osx it happended that it was installed but the PATHs were not set properly:
see https://www.reddit.com/r/QGIS/comments/1q7emaa/why_doesnt_grass_show_in_qgis_how_to_fix_it/ and this solution: