Add new requirement beautifulsoup4

To automatically prettify HTML files generated out of Jinja2
templates (I2f0c61006ef8885e157eb2b800080407f2bae393) in the
openstack-manuals repository when running the publishdocs job
we need to add the requirement beautifulsoup4.

Change-Id: Id1c15ea7ab5ef3295e0c14ef2b12ad96ef4acacc
Merge "Add new requirement beautifulsoup4"