The message "GSettings schema for the Projects Plugin is not installed. ..." shows up when the plugin is installed while gedit is running. A restart of gedit should resolve the issue.
Can you confirm that gedit was running while you installed the plugin?
In this case I would just improve the message to be more precise.
The message "GSettings schema for the Projects Plugin is not installed. ..." shows up when the plugin is installed while gedit is running. A restart of gedit should resolve the issue.
Can you confirm that gedit was running while you installed the plugin?
In this case I would just improve the message to be more precise.