loosen Pillow
dask[array]>=2.1.0
fsspec>=0.3.3
imageio>=2.5.0
-Pillow<=7.0.0 # not a direct dependency; remove once fixed
+Pillow!=7.1.* # not a direct dependency, but 7.1.0 and 7.1.1 broke imageio
ipykernel>=5.1.1
numpy>=1.10.0
qtpy>=1.7.0
