Remove duplicated code and make base64 error handling better

src/main.rs

@@ -13,7 +13,7 @@ mod set4;
 mod utils;
 
 fn main() {
-    const RUN_ALL: bool = false;
+    const RUN_ALL: bool = true;
     if RUN_ALL {
         set1::challenge1();
         set1::challenge2();