s3fs 0.5.x incompatibility with Python 3.6

What happened:
Using s3fs==0.5.1 and python 3.6.12 is not possible to push data on S3 using pandas 1.1.3. The function asyncio.current_task is only available since python 3.7 (see https://docs.python.org/3/library/asyncio-task.html#asyncio.current_task).

To be able to push data on S3, I had to downgrade to s3fs==0.4.2.

What you expected to happen:
When I call pip install s3fs I expected it selects a version compatible with Python 3.6.

Could you fix with a workaround on asyncio.current_task or specify in setup.py that requires Python >=3.7, please?

Minimal Complete Verifiable Example:

>>> import pandas
>>> df = ...
>>> df.to_csv("s3://.../file.csv", index=False)
...
/usr/local/anaconda3/envs/wonderful/lib/python3.6/site-packages/fsspec/asyn.py in _run_until_done(coro)
     19     loop = asyncio.get_event_loop()
     20     assert loop.is_running()
---> 21     task = asyncio.current_task()
     22     asyncio.tasks._unregister_task(task)
     23     current_task = asyncio.tasks._current_tasks.get(loop)

AttributeError: module 'asyncio' has no attribute 'current_task'

Anything else we need to know?:

Using s3fs==0.5.0 I had another unexpected behavior and we were not able to specifiy the aws region at the pandas.
Furthermore this is a regression compare to the 0.4.2 version.

>>> import pandas
>>> df = ...
>>> df.to_csv("s3://.../file.csv", index=False)
...
/usr/local/anaconda3/envs/wonderful/lib/python3.6/site-packages/s3fs/core.py in _mkdir(self, path, acl, create_parents, **kwargs)
    448                 self.invalidate_cache(bucket)
    449             except ClientError as e:
--> 450                 raise translate_boto_error(e) from e
    451             except ParamValidationError as e:
    452                 raise ValueError('Bucket create failed %r: %s' % (bucket, e))

PermissionError: The unspecified location constraint is incompatible for the region specific endpoint this request was sent to.

Environment:

• Dask version: no used
• Python version: python 3.6
• Operating System: mac os x
• Install method (conda, pip, source):
  • conda 4.8.3
  • pip 20.2.3
  • s3fs 0.5.1
  • pandas 1.1.3

Start by reproducing the Python 3.6 traceback from fsspec/asyn.py, then inspect setup.py for the supported Python versions. Review the related s3fs/core.py region error as a separate regression, and verify that both S3 uploads and region-specific bucket creation behave correctly on the supported versions.