Backport PR #13080: Pin pillow to < 5.4 to fix doc build

tacaswell · MeeseeksDev[bot] · commit 3c4dd0c304bb · 2019-01-02T16:03:04.000Z
diff --git a/doc-requirements.txt b/doc-requirements.txt
@@ -11,5 +11,5 @@ colorspacious
 ipython
 ipywidgets
 numpydoc>=0.8
-pillow>=3.4
+pillow>=3.4,<5.4
 sphinx-gallery>=0.2
