use Display for errors rather than Debug

src/main.rs

@@ -2235,7 +2235,7 @@ impl Page {
     }
 }
 
-fn main() -> Result<(), Box<dyn std::error::Error>> {
+fn main_inner() -> Result<(), Box<dyn std::error::Error>> {
     let args: Vec<String> = std::env::args().collect();
     let page_numbers: Option<Box<dyn Iterator<Item = NonZero<u32>>>> = if 2 < args.len() {
         Some(if let Some((start, end)) = args[2].split_once(":") {
@@ -2277,3 +2277,13 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     std::fs::write("powerisa-instructions.xml", output)?;
     Ok(())
 }
+
+fn main() -> std::process::ExitCode {
+    match main_inner() {
+        Ok(()) => std::process::ExitCode::SUCCESS,
+        Err(e) => {
+            println!("Error: {e}");
+            std::process::ExitCode::FAILURE
+        }
+    }
+}