Merge pull request #116 from pp-mo/linkcheck_testing

Fix deliberate error.

Author: pp-mo

.lycheeignore

@@ -46,7 +46,7 @@ https://www.flaticon.com
 https://www.thing.com
 
 # DEAD, todo:remove, used in docs/src/userguide/plotting_a_cube.rst
-#https://www.personal.psu.edu/cab38/ColorBrewer/ColorBrewer_updates.html
+https://www.personal.psu.edu/cab38/ColorBrewer/ColorBrewer_updates.html
 
 # nonfunctional, found in some code examples
 https://www.somehost.com