TST: Pin docutils in failing jobs

Author: pllim

tox.ini

@@ -15,8 +15,11 @@ deps =
     sphinx17: sphinx==1.7.*
     sphinx18: sphinx==1.8.*
     sphinx20: sphinx==2.0.*
+    sphinx20: docutils==0.17.*
     sphinx24: sphinx==2.4.*
+    sphinx24: docutils==0.17.*
     sphinx30: sphinx==3.0.*
+    sphinx30: docutils==0.17.*
     sphinx35: sphinx==3.5.*
     sphinx40: sphinx==4.0.*
     sphinxdev: git+https://github.com/sphinx-doc/sphinx#egg=sphinx