Reverted change made in 4a234de

Reverted due to this breaking `ia upload --remote-name` and
`ia upload --stdin`.

internetarchive/cli/ia_upload.py

@@ -86,18 +86,8 @@
 )
 
 
-def _check_files_exist(files):
-    return [
-        file for file in files
-        if Path(file).exists()
-    ]
-
-
 def _upload_files(item, files, upload_kwargs, prev_identifier=None, archive_session=None):
     """Helper function for calling :meth:`Item.upload`"""
-    # Exclude files that do not exist. (Make a copy of the list)
-    files = _check_files_exist(files)
-
     # Check if the list has any element.
     if not files:
         raise FileNotFoundError("No valid file was found. Check your paths.")