BUG: fix sphinx warning on sphinx v1.4

4 jobs for fix-warning-sphinx1.4 in 2 minutes and 32 seconds (queued for 1 second)
Status Job ID Name Coverage
  Precheck
canceled #2701
fast-build

00:02:32

 
  External
passed cdash:debian-unstable-gcc

passed cdash:otb-centos-superbuild-base

passed cdash:ubuntu-18.04-llvm