Investigate Error.

[btimby]

  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 293, in backend_from_fname
    mime = EXTS_TO_MIMETYPES[ext]
KeyError: ''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/btimby/Code/smartfile/duster/duster/__main__.py", line 117, in <module>
    main()
  File "/home/btimby/Code/smartfile/duster/duster/__main__.py", line 110, in main
    return crawl(path, **kw)
  File "/home/btimby/Code/smartfile/duster/duster/crawler.py", line 102, in crawl
    return cr.run()
  File "/home/btimby/Code/smartfile/duster/duster/crawler.py", line 97, in run
    self.process_dir_parallel(self.path)
  File "/home/btimby/Code/smartfile/duster/duster/crawler.py", line 80, in process_dir_parallel
    fps = fut.result()
  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 398, in result
    return self.__get_result()
  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 357, in __get_result
    raise self._exception
  File "/usr/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/btimby/Code/smartfile/duster/duster/crawler.py", line 24, in process_file
    for fp in fingerprints:
  File "/home/btimby/Code/smartfile/duster/duster/__init__.py", line 282, in dust
    for fn, type, size, ct, mt, raw, text in unwrap(path):
  File "/home/btimby/Code/smartfile/duster/duster/containers.py", line 242, in unwrap
    for item in unwrap_text(path, type):
  File "/home/btimby/Code/smartfile/duster/duster/containers.py", line 164, in unwrap_text
    text = fulltext.get(path, **kwargs)
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 374, in get
    backend=backend, kwargs=kwargs)
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 351, in _get
    text = fun(backend_mod, path_or_file, **kwargs)
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 230, in _get_path
    return backend._get_path(path, **kwargs)
  File "/home/btimby/Code/fulltext/fulltext/backends/__zip.py", line 20, in _get_file
    text.write(get(zf, name=name))
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 374, in get
    backend=backend, kwargs=kwargs)
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 326, in _get
    backend_mod = backend_from_fname(name)
  File "/home/btimby/Code/fulltext/fulltext/__init__.py", line 295, in backend_from_fname
    with open(name, 'rb') as f:
FileNotFoundError: [Errno 2] No such file or directory: '_rels/.rels'