Error on File Cleanup: The 'file' attribute has no file associated with it.
Created by: hixi
https://sentry.njo.ch/geometalab/osmaxxprod/issues/175/
ValueError: The 'file' attribute has no file associated with it.
File "osmaxx/excerptexport/management/commands/purge_old_result_files.py", line 57, in _remove_old_files
path = old_file.file.path