Change estimated error code when thread spawning fails

src/lib.rs

@@ -57,10 +57,10 @@ pub unsafe extern "C" fn pthread_create(
 
     if handle.is_null() {
         // There was some error, but libctru doesn't expose the result.
-        // We assume there was an incorrect parameter (such as too low of a priority).
+        // We assume there was permissions issue (such as too low of a priority).
         // We also need to clean up the closure at this time.
         drop(Box::from_raw(main));
-        return libc::EINVAL;
+        return libc::EPERM;
     }
 
     *native = handle as _;