message: Pin mistune to pre-2.x to fix doc build
diff: @@ -11,3 +11,6 @@ furo
  # docutils 0.18.0 causes "AttributeError: 'Values' object
  # has no attribute 'section_self_link'" error when building doc
  docutils==0.17.*
  +# mistune 2.0.0-rc1 causes "AttributeError: module 'mistune'
  +# has no attribute 'BlockGrammar'" error when building doc
  +mistune<2.0.0
  \ No newline at end of file
  