[Python] test_move_file() is failed with fsspec 0.8.0

================================== FAILURES ===================================
__ test_move_file[PyFileSystem(FSSpecHandler(fsspec.filesystem("memory")))] ___
fs = <pyarrow._fs.PyFileSystem object at 0x0000003D057AA520>
pathfn = <function py_fsspec_memoryfs.<locals>.<lambda> at 0x0000003D04F70B58>
    def test_move_file(fs, pathfn):
        s = pathfn('test-move-source-file')
        t = pathfn('test-move-target-file')
    
        with fs.open_output_stream(s):
            pass
    
>       fs.move(s, t)
pyarrow\tests\test_fs.py:798: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
pyarrow\_fs.pyx:519: in pyarrow._fs.FileSystem.move
    check_status(self.fs.Move(source, destination))
pyarrow\_fs.pyx:1024: in pyarrow._fs._cb_move
    handler.move(frombytes(src), frombytes(dest))
pyarrow\fs.py:199: in move
    self.fs.mv(src, dest, recursive=True)
C:\Miniconda37-x64\envs\arrow\lib\site-packages\fsspec\spec.py:744: in mv
    self.copy(path1, path2, recursive=recursive, maxdepth=maxdepth)
C:\Miniconda37-x64\envs\arrow\lib\site-packages\fsspec\spec.py:719: in copy
    self.cp_file(p1, p2, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <fsspec.implementations.memory.MemoryFileSystem object at 0x0000003D01096A78>
path1 = 'test-move-source-file/', path2 = 'test-move-target-file/'
kwargs = {'maxdepth': None}
    def cp_file(self, path1, path2, **kwargs):
        if self.isfile(path1):
>           self.store[path2] = MemoryFile(self, path2, self.store[path1].getbuffer())
E           KeyError: 'test-move-source-file/'
C:\Miniconda37-x64\envs\arrow\lib\site-packages\fsspec\implementations\memory.py:134: KeyError