DOC/CI: temp pin matplotlib for doc build (pandas-dev#20045)

jorisvandenbossche · pandres · commit d45df389a6c3 · 2018-03-10T09:53:15.000-06:00
diff --git a/ci/requirements-3.6_DOC.run b/ci/requirements-3.6_DOC.run
@@ -5,7 +5,7 @@ sphinx
 nbconvert
 nbformat
 notebook
-matplotlib
+matplotlib=2.1*
 seaborn
 scipy
 lxml
