printing missing binary in the case something is missing. testing later

src/app/build/asciidoctor.rs

@@ -12,9 +12,11 @@ fn exec_command(command: &mut process::Command) -> Result<(), String> {
         }
     } else {
         println!("{}", result.unwrap_err());
-        return Err(
-            "asciidoctor not installed. For more information run docki health!".to_string(),
-        );
+        let binary_name = command.get_args().next();
+        return Err(format!(
+            "{} not installed. For more information run docki health!",
+            binary_name.unwrap_or("Something is")
+        ));
     }
 }