Use fsspec master (for now)

Martin Durant · Martin Durant · commit cd0f96f7f2b0 · 2020-09-17T11:36:42.000-04:00
diff --git a/requirements_dev_optional.txt b/requirements_dev_optional.txt
@@ -18,6 +18,7 @@ pytest-cov==2.7.1
 pytest-doctestplus==0.4.0
 pytest-remotedata==0.3.2
 h5py==2.10.0
-s3fs==0.5.0; python_version > '3.6'
+s3fs==0.5.1; python_version > '3.6'
+git+https://github.com/intake/filesystem_spec; python_version > '3.6'
 moto>=1.3.14; python_version > '3.6'
 flask
