1. Created a fresh 12.04.4 server VM
2. Installed SchoolTool 2.6.4 from ppa:schooltool-owners/dev
3. Upgraded the VM to 14.04
4. Installed SchoolTool 2.8.3 from ppa:schooltool-owners/2.8
The custom-css directory and custom.css files were created correctly.
FWIW, this procedure worked for me:
1. Created a fresh 12.04.4 server VM owners/ dev owners/ 2.8
2. Installed SchoolTool 2.6.4 from ppa:schooltool-
3. Upgraded the VM to 14.04
4. Installed SchoolTool 2.8.3 from ppa:schooltool-
The custom-css directory and custom.css files were created correctly.