ncurses: panic with error message if $TERM is unset

src/backend/curses/n.rs

@@ -59,6 +59,14 @@ fn write_to_tty(bytes: &[u8]) -> io::Result<()> {
 impl Backend {
     /// Creates a new ncurses-based backend.
     pub fn init() -> Box<dyn backend::Backend> {
+        // Check the $TERM variable.
+        if std::env::var("TERM")
+            .map(|var| var.is_empty())
+            .unwrap_or(true)
+        {
+            panic!("$TERM is unset. Cannot initialize ncurses interface.");
+        }
+
         // Change the locale.
         // For some reasons it's mandatory to get some UTF-8 support.
         ncurses::setlocale(ncurses::LcCategory::all, "");