html_static_path is a kind of source directory and it was set to
destination directory (../html) which caused infinite recursion with
Sphinx 1.2 and above.
# Add any paths that contain custom static files (such as style sheets) here,
# relative to this directory. They are copied after the builtin static files,
# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['../html']
+html_static_path = []
# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
# using the given strftime format.