Don't use trait objects without an explicit dyn

src/sdl2/ttf/context.rs

@@ -96,7 +96,7 @@ impl error::Error for InitError {
         }
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         match *self {
             InitError::AlreadyInitializedError => {
                 None

src/sdl2/ttf/font.rs

@@ -69,7 +69,7 @@ impl error::Error for FontError {
         }
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         match *self {
             FontError::InvalidLatin1Text(ref error) => {
                 Some(error)