doc: fix configuration to build on RTD

Add module to path.

Mock the C wrapper.

Signed-off-by: Matteo Cafasso <noxdafox@gmail.com>

doc/conf.py

@@ -17,9 +17,14 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-# import os
-# import sys
-# sys.path.insert(0, os.path.abspath('.'))
+import os
+import sys
+from unittest.mock import MagicMock
+
+module_dir = os.path.abspath(
+    os.path.join(os.path.dirname(os.path.realpath(__file__)), os.pardir))
+sys.path.insert(0, module_dir)
+sys.modules['clips._clips'] = MagicMock()
 
 # -- General configuration ------------------------------------------------