[Docs] Add missing requirement (#8238)

Our docs do not build without the `sphinx-rtd-theme` package. This
commit adds the module as an explicit requirement such that if the
module is missing, building the docs fails when configuring and with a
useful error message.

diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt
index e37183f90904ff410261c371a18de06eefd684cf..e205d59b74f82d3e0893dea48a39f59a37bd721b 100644 (file)
--- a/docs/CMakeLists.txt
+++ b/docs/CMakeLists.txt
@@ -17,6 +17,7 @@ check_python_module(breathe)
 check_python_module(sphinxcontrib.bibtex sphinxcontrib-bibtex)
 check_python_module(sphinx_tabs.tabs sphinx-tabs)
 check_python_module(sphinxcontrib.programoutput sphinxcontrib.programoutput)
+check_python_module(sphinx_rtd_theme sphinx-rtd-theme)
 
 add_subdirectory(api)