fix error message

Author: magiclen

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "xcompress"
-version = "0.10.0"
+version = "0.10.1"
 authors = ["Magic Len <len@magiclen.org>"]
 repository = "https://github.com/magiclen/xcompress"
 homepage = "https://magiclen.org/xcompress"

src/lib.rs

@@ -438,7 +438,7 @@ impl Config {
                             path
                         }
                         Err(_) => {
-                            return Err(String::from("FFMPEG_PATH is incorrect."));
+                            return Err(format!("{} is incorrect.", name));
                         }
                     };