Fix walk

[mnarodovitch]

/usr/local/lib/python3.7/site-packages/pyarrow/filesystem.py:412: RuntimeWarning: coroutine 'S3FileSystem._ls' was never awaited
  for key in list(self.fs._ls(path, refresh=refresh)):
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

see
https://github.com/dask/s3fs/blob/master/s3fs/core.py#L657
for reference

[mnarodovitch]

related: fsspec/s3fs#366

[jorisvandenbossche]

@michaelnarodovitch thanks for the fix, but this is already fixed on master by not using the S3FSWrapper class at all anymore (see #8557 and #8627).

Unfortunately we didn't do a bug fix release with it, so for now you need to either pin pyarrow to 1.0.0, or either pin fsspec to 0.4 when using pyarrow 2.0.0. A new pyarrow release with the fix (pyarrow 3.0.0) will be out in a week or two.

[mnarodovitch]

That's great. Thank you so much!