Change eprintln -> warning

I added another brace block to the warning macro
because I was getting a compile error without them.

src/main.rs

@@ -138,7 +138,7 @@ fn main() {
     if opt.open_in_browser {
         match open::that(output_path) {
             Ok(_) => (),
-            Err(_) => eprintln!("There was an error opening the browser."),
+            Err(_) => warning!("There was an error opening the browser."),
         }
     }
 }

src/util.rs

@@ -19,8 +19,10 @@ macro_rules! error {
 
 macro_rules! warning {
     ($fmt:expr) => {
-        use colored::*;
-        println!(concat!("{}: ", $fmt), if cfg!(windows) { "warning".normal() } else { "warning".bold().yellow() });
+        {
+            use colored::*;
+            println!(concat!("{}: ", $fmt), if cfg!(windows) { "warning".normal() } else { "warning".bold().yellow() });
+        }
     };
     ($fmt:expr, $($arg:tt)*) => {
         use colored::*;