sphinx: report errors when dependencies are not met

To build the Sphinx documentation, we have the following dependencies:
* sphinx
* sphinx_rtd_theme
* pyyaml

If any of these dependencies are missing, we might end up with some
cryptic error messages. This patch adds better error reporting when
dependencies are not met.

(From yocto-docs rev: 19df8d1ec56dc2ecb44122288cc53e84237fab69)

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/documentation/conf.py b/documentation/conf.py
index 34d1bc97a4..f2dd2556fa 100644
--- a/documentation/conf.py
+++ b/documentation/conf.py
@@ -91,10 +91,16 @@ intersphinx_mapping = {
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
-html_theme = 'sphinx_rtd_theme'
-html_theme_options = {
-    'sticky_navigation': False,
-}
+try:
+    import sphinx_rtd_theme
+    html_theme = 'sphinx_rtd_theme'
+    html_theme_options = {
+        'sticky_navigation': False,
+    }
+except ImportError:
+    sys.stderr.write("The Sphinx sphinx_rtd_theme HTML theme was not found.\
+    \nPlease make sure to install the sphinx_rtd_theme python package.\n")
+    sys.exit(1)
 
 html_logo = 'sphinx-static/YoctoProject_Logo_RGB.jpg'