UPath broken in Python 3.11

[dtrifiro]

In Python 3.11 (currently slated for release in October 2022), pathlib accessors have been removed (see https://bugs.python.org/issue43012), resulting in UPath breaking.

For example, with an s3 remote mocked with moto (pip install moto[server])

$ moto_server s3                                                                                             
 * Running on http://127.0.0.1:5000 (Press CTRL+C to quit)

from upath import UPath
path = UPath("s3://bucketname")
path.mkdir()

FileNotFoundError                         Traceback (most recent call last)

----> 1 u.mkdir()

File /usr/lib/python3.10/pathlib.py:1175, in Path.mkdir(self, mode, parents, exist_ok)
   1171 """
   1172 Create a new directory at this given path.
   1173 """
   1174 try:
-> 1175     self._accessor.mkdir(self, mode)
   1176 except FileNotFoundError:
   1177     if not parents or self.parent == self:

FileNotFoundError: [Errno 2] No such file or directory: 's3://bucketname/'

or, trying to write something to a file:

f = path / "file"
f.write_text("ciao")

Traceback (most recent call last)
----> 1 f.write_text("ciao")

File /usr/lib/python3.10/pathlib.py:1154, in Path.write_text(self, data, encoding, errors, newline)
   1151     raise TypeError('data must be str, not %s' %
   1152                     data.__class__.__name__)
   1153 encoding = io.text_encoding(encoding)
-> 1154 with self.open(mode='w', encoding=encoding, errors=errors, newline=newline) as f:
   1155     return f.write(data)

File universal_pathlib/upath/core.py:168, in UPath.open(self, *args, **kwargs)
    167 def open(self, *args, **kwargs):
--> 168     return self.fs.open(self, *args, **kwargs)

File universal_pathlib/upath/core.py:122, in UPath.__getattr__(self, item)
    120     return _accessor
    121 else:
--> 122     raise AttributeError(item)

AttributeError: fs