[sphinx] Fixed warnings

doc/conf.py

@@ -25,6 +25,7 @@ extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.napoleon',
     'sphinx.ext.viewcode',
+    'matplotlib.sphinxext.plot_directive',
     ]
 
 import sphinx
@@ -239,7 +240,8 @@ autodoc_default_flags = [
 from bob.extension.utils import link_documentation, load_requirements
 sphinx_requirements = "extra-intersphinx.txt"
 if os.path.exists(sphinx_requirements):
-    intersphinx_mapping = link_documentation(additional_packages=load_requirements(sphinx_requirements))
+    intersphinx_mapping = link_documentation(additional_packages=
+                                             ['python', 'numpy'] + load_requirements(sphinx_requirements))
 else:
     intersphinx_mapping = link_documentation()