Trying to see if this is the reason why macOS fails

Author: MomIsBestFriend

ci/deps/azure-macos-36.yaml

@@ -24,7 +24,7 @@ dependencies:
   - openpyxl
   - pyarrow>=0.13.0
   - pytables
-  - python-dateutil==2.6.1
+  - python-dateutil=2.6.1
   - pytz
   - xarray
   - xlrd