I was trying to get this to work a little while ago but never found the cause myself. The problem is that a value set (regardless of the value) results in rejection. There may be a different standard to solve this issue as other packages sometimes allow these types of selections.
e.g. echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | sudo /usr/bin/debconf-set-selections
This very helpful individual already suggested a fix (not through these channels, found nothing while searching):
https://www.mail-archive.com/[email protected]/msg1288649.html
I was trying to get this to work a little while ago but never found the cause myself. The problem is that a value set (regardless of the value) results in rejection. There may be a different standard to solve this issue as other packages sometimes allow these types of selections.
e.g.
echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | sudo /usr/bin/debconf-set-selections