Allow unused imports for cargo test

src/main.rs

@@ -1,12 +1,11 @@
 #![feature(panic_implementation)] // required for defining the panic handler
 #![no_std] // don't link the Rust standard library
 #![cfg_attr(not(test), no_main)] // disable all Rust-level entry points
-#![cfg_attr(test, allow(dead_code, unused_macros))] // allow unused code in test mode
+#![cfg_attr(test, allow(dead_code, unused_macros, unused_imports))]
 
 #[macro_use]
 extern crate blog_os;
 
-#[cfg(not(test))]
 use core::panic::PanicInfo;
 
 /// This function is the entry point, since the linker looks for a function