PDF documentation build

Based on https://review.opendev.org/#/c/601659/ and
https://review.opendev.org/#/c/664555/

The generated PDF file is found at the top directory of the job log.

Story: 2006084
Task: 34864
Depends-On: https://review.opendev.org/664555
Change-Id: I5e25f1dfbec22b26d42eff3c6776a2d01e90bc60

doc/source/conf.py

@@ -236,7 +236,7 @@ htmlhelp_basename = 'Horizondoc'
 # (source start file, target name, title, author, documentclass
 # [howto/manual]).
 latex_documents = [
-    ('index', 'Horizon.tex', u'Horizon Documentation',
+    ('index', 'doc-horizon.tex', u'Horizon Documentation',
      u'OpenStack Foundation', 'manual'),
 ]
 
@@ -258,8 +258,16 @@ latex_documents = [
 # latex_appendices = []
 
 # If false, no module index is generated.
-# latex_domain_indices = True
+latex_domain_indices = False
 
+latex_elements = {
+    'makeindex': '',
+    'printindex': '',
+    'preamble': r'\setcounter{tocdepth}{3}',
+}
+
+# Disable usage of xindy https://bugzilla.redhat.com/show_bug.cgi?id=1643664
+latex_use_xindy = False
 
 # -- Options for manual page output -------------------------------------------
 

doc/source/index.rst

@@ -68,5 +68,7 @@ Information
 
    glossary
 
-* :ref:`genindex`
+.. only:: html
-* :ref:`modindex`
+
+   * :ref:`genindex`
+   * :ref:`modindex`

tox.ini

@@ -152,6 +152,16 @@ deps =
 commands =
   sphinx-build -W -b html doc/source doc/build/html
 
+[testenv:pdf-docs]
+basepython = python3
+envdir = {toxworkdir}/docs
+deps = {[testenv:docs]deps}
+whitelist_externals =
+  make
+commands =
+  sphinx-build -W -b latex doc/source doc/build/pdf
+  make -C doc/build/pdf
+
 [testenv:releasenotes]
 basepython = python3
 envdir = {toxworkdir}/docs