ssh filesystem and put_file are incompatible

Using a ssh filesystem and put_files gives an error

import fsspec
import sshfs
fs = fsspec.filesystem("ssh", host='xx.xx.xx.xx', username='eouser') 
fs.put_file(lpath="t", rpath="/home/me/t")

I receive an exception:

File "/home/me/miniconda3/envs/olci/lib/python3.9/site-packages/fsspec/callbacks.py", line 66, in relative_update
    self.value += inc
TypeError: unsupported operand type(s) for +=: 'int' and 'NoneType'

The reason is because the 'write' method in paramiko does not return the length of written data.
https://github.com/jbouse-debian/paramiko/blob/master/paramiko/file.py#L385

Unless paramiko changes their function, the method 'put_file' in spec.py should test segment_len to be None and skip the update... or use len(data) as a default as follows:

                    segment_len = f2.write(data)
                    if segment_len is None:
                          segment_len = len(data)
                    callback.relative_update(segment_len)

I'm not sure if this is a good solution...

Start in spec.py at put_file, then inspect fsspec/callbacks.py and the Paramiko file.py write behavior linked in the report. Reproduce the SSH transfer with the provided example and verify that a write returning None no longer causes the callback TypeError while the transfer completes.