To reproduce:
- edit any Elisp file, but don't save it;
- open its directory in Dired;
- evaluate `(package-dir-info)'.
Fails with: (file-missing "Opening input file" "No such file or directory" ".../.#blabla.el")
I.e. it tries to open the lock created for the unsaved file as a normal file and fails. I'm not 100% sure this should be considered a bug, but from my point of view it is so. Even if this is not a bug, the function should probably fail with a more descriptive error.
Paul