fix when no version

Author: Martin Durant

fsspec/spec.py

@@ -2,7 +2,6 @@
 import logging
 import os
 import warnings
-from distutils.version import LooseVersion
 from errno import ESPIPE
 from hashlib import sha256
 from glob import has_magic
@@ -12,6 +11,7 @@
 from .utils import (
     read_block,
     tokenize,
+    loose_version,
     stringify_path,
     other_paths,
     get_package_version_without_import,
@@ -79,7 +79,7 @@ def __call__(cls, *args, **kwargs):
 
 
 pa_version = get_package_version_without_import("pyarrow")
-if LooseVersion(pa_version) < LooseVersion("2.0"):
+if pa_version and loose_version(pa_version) < loose_version("2.0"):
     import pyarrow as pa
 
     up = pa.filesystem.DaskFileSystem