try to fix CI

Author: emmanuelle

packages/python/plotly/tox.ini

@@ -60,6 +60,7 @@ deps=
     pandas==0.24.2
     xarray==0.10.9
     statsmodels==0.10.2
+    pillow==5.2.0
     backports.tempfile==1.0
     optional: --editable=file:///{toxinidir}/../plotly-geo
     optional: numpy==1.16.5
@@ -71,7 +72,6 @@ deps=
     optional: shapely==1.7.0
     optional: geopandas==0.3.0
     optional: pyshp==1.2.10
-    optional: pillow==5.2.0
     optional: matplotlib==2.2.3
     optional: scikit-image==0.14.4
     optional: kaleido