Add tox environment to generate HTML test case reports.

By typing below commands it generates HTML report file
of Python test case results:

 tox -e report

It generates 'report/build/testr_results.html' file.

To run test cases (for example scenario tests) and produce
report HTML file it is possible to chain tox environment
names in a list. For example:

 tox -e scenario,report

Or simply:

 tox -e scenario
 tox -e report

This new environment is intended to be used in CI jobs
to produce reports after verifications.

Change-Id: I63d4d2977fb5b2c868361aa00db0e1334f33fa10

report/.gitignore

@@ -0,0 +1 @@
+/build/

report/build.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# Produce test HTML report file into ${REPORT_DIR}
+
+set -xeu
+
+
+TESTR_DIR=${TESTR_DIR:-$(pwd)}
+BUILD_DIR=${BUILD_DIR:-${TESTR_DIR}/report/build}
+SUBUNIT_FILE=${SUBUNIT_FILE:-${BUILD_DIR}/last.subunit}
+TESTR_RESULTS_HTML=${TESTR_RESULTS_HTML:-${BUILD_DIR}/testr_results.html}
+
+make_testr_results_html() {
+    mkdir -p "$(dirname ${SUBUNIT_FILE})"
+    (cd "${TESTR_DIR}" && stestr last --subunit) > "${SUBUNIT_FILE}"
+    (cd "${BUILD_DIR}" && subunit2html "${SUBUNIT_FILE}" "${TESTR_RESULTS_HTML}")
+}
+
+make_testr_results_html

report/requirements.txt

@@ -0,0 +1,4 @@
+# Requirements file for 'report' Tox environment
+
+os-testr>=1.0   # Apache 2.0
+stestr>=2.0     # Apache-2.0

tox.ini

@@ -143,7 +143,7 @@ whitelist_externals = *
 commands = {posargs}
 
 
-# --- documentation environments ---------------------------------------------
+# --- documentation environments ----------------------------------------------
 
 [testenv:docs]
 
@@ -169,3 +169,9 @@ deps = {[testenv:docs]deps}
 commands =
     sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
+
+# --- CI report environments --------------------------------------------------
+
+[testenv:report]
+deps = -r {toxinidir}/report/requirements.txt
+commands = {toxinidir}/report/build.sh