message: Display detailed error in FsCacheHandler constructor when cachefiles device not ready.
  Files: fs_cache.rs
diff: @@ -250,7 +250,12 @@ impl FsCacheHandler {
  .write(true)
  .read(true)
  .create(false)
  - .open(path)?;
  + .open(path)
  + .map_err(|e| {
  + error!("Failed to open cachefiles device {}. {}", path, e);
  + e
  + })?;
  +
  let poller =
  Poll::new().map_err(|_e| eother!("fscache: failed to create poller for service"))?;
  let waker = Waker::new(poller.registry(), Token(TOKEN_EVENT_WAKER))
  