Mock all external dependencies when building docs

docs/conf.py

@@ -13,6 +13,42 @@
 
 import sys, os
 
+class Mock(object):
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def __call__(self, *args, **kwargs):
+        return Mock()
+
+    @classmethod
+    def __getattr__(self, name):
+        if name in ('__file__', '__path__'):
+            return '/dev/null'
+        elif name[0] == name[0].upper():
+            return type(name, (), {})
+        else:
+            return Mock()
+
+MOCK_MODULES = [
+    'alsaaudio',
+    'dbus',
+    'dbus.mainloop',
+    'dbus.mainloop.glib',
+    'dbus.service',
+    'glib',
+    'gobject',
+    'gst',
+    'pygst',
+    'pykka',
+    'pykka.actor',
+    'pykka.future',
+    'pykka.registry',
+    'pylast',
+    'serial',
+]
+for mod_name in MOCK_MODULES:
+    sys.modules[mod_name] = Mock()
+
 # If extensions (or modules to document with autodoc) are in another directory,
 # 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.