PDF Documentation Build tox target

This patch adds a `pdf-docs` tox target that will build
PDF versions of our docs. As per the Train community goal:

  https://governance.openstack.org/tc/goals/selected/train/pdf-doc-generation.html

Story: 2006122
Task: 35514
Change-Id: I7e0ee410ac603774e4b03f859ac3aa20e5afc9b8

doc/source/conf.py

@@ -181,7 +181,7 @@ htmlhelp_basename = 'SwiftClientwebdoc'
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto/manual])
 latex_documents = [
-    ('index', 'SwiftClient.tex', u'SwiftClient Documentation',
+    ('index', 'doc-python-swiftclient.tex', u'SwiftClient Documentation',
      u'OpenStack, LLC.', 'manual'),
 ]
 
@@ -201,3 +201,5 @@ latex_documents = [
 
 # If false, no module index is generated.
 # latex_use_modindex = True
+
+latex_use_xindy = False

tox.ini

@@ -109,3 +109,12 @@ deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
   .[keystone]
+
+[testenv:pdf-docs]
+basepython = python3
+deps = {[testenv:docs]deps}
+whitelist_externals =
+  make
+commands =
+  sphinx-build -W -b latex doc/source doc/build/pdf
+  make -C doc/build/pdf