The is one of community goals that each project should produce a
single PDF file. The pdf should be in the output of openstack-tox-docs
job.

TeX packages are required to build PDF locally, following is
recommended:

* inkscape
* texlive-latex-base
* texlive-latex-extra
* texlive-fonts-recommended

More about the goal:
https://governance.openstack.org/tc/goals/train/pdf-doc-generation.html
https://etherpad.openstack.org/p/train-pdf-support-goal
https://etherpad.openstack.org/p/pdf-goal-train-common-problems

Change-Id: Ia0f8b73bcbda6295319f5c8de1aa02a40844207b