Adds upstream training to OpenStack gate

Update the current gate 'slides' to build and publish upstream
training content. This patch does the following changes.

* Adds generateslides script to use sphinx/hieroglyph to build slides
* Updates tox.ini to use generateslides script
* Update .gitignore to ignore _build/ directory which is the default
  folder for generated output generated by sphix.

Hence forth, any changes to the upstream training rst slides will be
gated and published, also it is essential to note that these jobs are
new and may not be accurate or reliable to address all the errors in
the rst slides.

Change-Id: I8a220dd31501f9b3733a6282d7048fe283d2a0d1

.gitignore

@@ -8,6 +8,7 @@ publish-docs/
 generated/
 /build-*.log.gz
 build/
+_build/
 
 # Ignore Vagrant Related Files
 acceptance_config.yml

tools/generateslides

@@ -0,0 +1,7 @@
+#!/bin/bash
+# Used by tox.ini when checking build and publishing docs to website
+
+# Generate and publish upstream training slides
+
+mkdir -p publish-docs/trunk/training-guides/upstream-training/
+sphinx-build -b slides doc/upstream-training/source/ publish-docs/trunk/training-guides/upstream-training/

tox.ini

@@ -28,12 +28,12 @@ commands =
   mkdir -p publish-docs/trunk/training-guides
   # Build training labs scripts
   bash {toxinidir}/tools/generatelabs
+  bash {toxinidir}/tools/generateslides
 
 [doc8]
 # Settings for doc8:
 # File extensions to use
 extension = .rst,.txt
-# Directories/files to ignore
 ignore-path = doc/*/build/*
 
 [testenv:upstream-slides]