1. Sphinx 1.8 introduced [1] the '--keep-going' argument which, as its name
suggests, keeps the build running when it encounters non-fatal errors.
This is exceptionally useful in avoiding a continuous edit-build loop
when undertaking large doc reworks where multiple errors may be
introduced.
2. Remove the exists folder before run sphinx-build command
[1] https://github.com/sphinx-doc/sphinx/commit/e3483e9b045
Change-Id: I1b1b45bf3ae104defbb16282e18995a28f67f649
676b38a9ad