Use StorageError::CustomError for implementations-specific (I/O) errors

libraries/persistent_store/src/storage.rs

@@ -34,17 +34,12 @@ pub enum StorageError {
 
     /// Implementation-specific error.
     CustomError,
-
-    // I/O error
-    #[cfg(feature = "hostenv")]
-    IOError,
 }
 
-#[cfg(feature = "hostenv")]
-#[allow(unused_variables)]
+#[cfg(feature = "std")]
 impl From<std::io::Error> for StorageError {
-    fn from(error: std::io::Error) -> Self {
-        Self::IOError
+    fn from(_: std::io::Error) -> Self {
+        Self::CustomError
     }
 }