download a folder using recursive gives FileNotFoundError but works

What happened:

I was debugging something over at aldfs (https://github.com/dask/adlfs/issues/120) and wanted to see the behavior of s3fs.

What you expected to happen:

I download a folder to local.

Minimal Complete Verifiable Example:

This downloads the remote folder '00' to a local folder '00

import s3fs
fs = s3fs.S3FileSystem(anon=True)
fs.get("noaa-goes16/ABI-L2-MCMIPC/2020/001/00", "00", recursive=True)

This returns

>>> fs.get("noaa-goes16/ABI-L2-MCMIPC/2020/001/00", "00", recursive=True)
Traceback (most recent call last):
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/s3fs/core.py", line 207, in _call_s3
    return await method(**additional_kwargs)
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/aiobotocore/client.py", line 151, in _make_api_call
    raise error_class(parsed_response, operation_name)
botocore.errorfactory.NoSuchKey: An error occurred (NoSuchKey) when calling the GetObject operation: The specified key does not exist.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/fsspec/asyn.py", line 278, in get
    return sync(self.loop, self._get, rpaths, lpaths)
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/fsspec/asyn.py", line 68, in sync
    raise exc.with_traceback(tb)
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/fsspec/asyn.py", line 52, in f
    result[0] = await future
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/fsspec/asyn.py", line 263, in _get
    return await asyncio.gather(
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/s3fs/core.py", line 694, in _get_file
    resp = await self._call_s3(
  File "/Users/Ray/miniconda3/envs/main/lib/python3.8/site-packages/s3fs/core.py", line 225, in _call_s3
    raise translate_boto_error(err) from err
FileNotFoundError: The specified key does not exist.

However, the process still runs in the background and gives the desired output.

Anything else we need to know?:

Environment:

• Dask version: 2.29.0
• Python version: 3.8.5
• Operating System: Mac
• Install method (conda, pip, source): Conda

Start in s3fs/core.py at _get_file and compare it with the fsspec/asyn.py _get path shown in the traceback. Reproduce the recursive fs.get call against the NOAA S3 path, then trace why a FileNotFoundError is raised even though the folder is downloaded. Done means the recursive download completes without the misleading exception.