BUG: read_csv stopped working with s3 file system
- [yes ] I have checked that this issue has not already been reported.

- [ yes ] I have confirmed this bug exists on the latest version of pandas.

- [ yes] (optional) I have confirmed this bug exists on the master branch of pandas.
Checked against pandas 1.1.0.dev0+1732.g2428cdda3


#### Problem description

read_csv in pandas1.0.4 has stopped working with s3fs.

On pandas1.0.3

```python
import pandas as pd; import s3fs
s3fs.S3FileSystem(anon=False, key=os.environ.get("STORE_USERNAME"), secret=os.environ.get("STORE_PASSWORD"))
df = pd.read_csv(filepath_or_buffer="s3://my-private-bucket/my_dataframe.csv")
print(df.shape)
```
prints the correct output, whilst using pandas1.0.4 it raises the following exception

```python
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/nico/.local/lib/python3.7/site-packages/pandas/io/parsers.py", line 676, in parser_f
    return _read(filepath_or_buffer, kwds)
  File "/home/nico/.local/lib/python3.7/site-packages/pandas/io/parsers.py", line 431, in _read
    filepath_or_buffer, encoding, compression
  File "/home/nico/.local/lib/python3.7/site-packages/pandas/io/common.py", line 212, in get_filepath_or_buffer
    filepath_or_buffer, encoding=encoding, compression=compression, mode=mode
  File "/home/nico/.local/lib/python3.7/site-packages/pandas/io/s3.py", line 52, in get_filepath_or_buffer
    file, _fs = get_file_and_filesystem(filepath_or_buffer, mode=mode)
  File "/home/nico/.local/lib/python3.7/site-packages/pandas/io/s3.py", line 42, in get_file_and_filesystem
    file = fs.open(_strip_schema(filepath_or_buffer), mode)
  File "/home/nico/.local/lib/python3.7/site-packages/fsspec/spec.py", line 775, in open
    **kwargs
  File "/home/nico/.local/lib/python3.7/site-packages/s3fs/core.py", line 378, in _open
    autocommit=autocommit, requester_pays=requester_pays)
  File "/home/nico/.local/lib/python3.7/site-packages/s3fs/core.py", line 1097, in __init__
    cache_type=cache_type)
  File "/home/nico/.local/lib/python3.7/site-packages/fsspec/spec.py", line 1065, in __init__
    self.details = fs.info(path)
  File "/home/nico/.local/lib/python3.7/site-packages/s3fs/core.py", line 530, in info
    Key=key, **version_id_kw(version_id), **self.req_kw)
  File "/home/nico/.local/lib/python3.7/site-packages/s3fs/core.py", line 200, in _call_s3
    return method(**additional_kwargs)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/client.py", line 316, in _api_call
    return self._make_api_call(operation_name, kwargs)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/client.py", line 622, in _make_api_call
    operation_model, request_dict, request_context)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/client.py", line 641, in _make_request
    return self._endpoint.make_request(operation_model, request_dict)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/endpoint.py", line 102, in make_request
    return self._send_request(request_dict, operation_model)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/endpoint.py", line 132, in _send_request
    request = self.create_request(request_dict, operation_model)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/endpoint.py", line 116, in create_request
    operation_name=operation_model.name)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/hooks.py", line 356, in emit
    return self._emitter.emit(aliased_event_name, **kwargs)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/hooks.py", line 228, in emit
    return self._emit(event_name, kwargs)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/hooks.py", line 211, in _emit
    response = handler(**kwargs)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/signers.py", line 90, in handler
    return self.sign(operation_name, request)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/signers.py", line 160, in sign
    auth.add_auth(request)
  File "/home/nico/.local/lib/python3.7/site-packages/botocore/auth.py", line 357, in add_auth
    raise NoCredentialsError
botocore.exceptions.NoCredentialsError: Unable to locate credentials
```

#### Output of ``pd.show_versions()``
using pandas 1.0.3

<details>
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.3.0-46-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : es_AR.UTF-8
LOCALE           : es_AR.UTF-8

pandas           : 1.0.3
numpy            : 1.18.4
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 9.0.1
setuptools       : 39.0.1
Cython           : None
pytest           : 5.4.0
hypothesis       : None
sphinx           : 1.6.7
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : 0.999999999
pymysql          : None
psycopg2         : None
jinja2           : 2.10
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : 5.4.0
pyxlsb           : None
s3fs             : 0.4.2
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None
</details>

using pandas 1.0.4
<details>
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.3.0-46-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : es_AR.UTF-8
LOCALE           : es_AR.UTF-8

pandas           : 1.0.4
numpy            : 1.18.4
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 9.0.1
setuptools       : 39.0.1
Cython           : None
pytest           : 5.4.0
hypothesis       : None
sphinx           : 1.6.7
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : 0.999999999
pymysql          : None
psycopg2         : None
jinja2           : 2.10
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : 5.4.0
pyxlsb           : None
s3fs             : 0.4.2
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None

</details>
