Fix 'Module index' broken HTTP link

'Module Index' link points to HTML doc generated from source/api
RST files. These RST files are generated by pbr, by setting the
parameter 'autodoc_index_modules' to True.

Partial-Bug: #1535244
Change-Id: Ifceb5a140599d3968ea3d353b12c0bbe99d955e6

tox.ini

@@ -20,12 +20,14 @@ commands =
 commands = flake8
 
 [testenv:venv]
+setenv = PYTHONHASHSEED=0
 commands = {posargs}
 
 [testenv:cover]
 commands = python setup.py testr --coverage --omit="watcher/tests/*" --testr-args='{posargs}'
 
 [testenv:docs]
+setenv = PYTHONHASHSEED=0
 commands = python setup.py build_sphinx
 
 [testenv:debug]