Add tox wrapper to fetch neutron

This is a clone of networking-sfc's tools/tox_install.sh
that allows the optimal version of neutron to be installed
when running tox.

Related commit: 10cecb9837d5f8563b5a2f0de6d1081cbde05bdb

Change-Id: I28230acb499c8aa04033fa552da660ec80c4fd03

tools/tox_install.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+# Many of neutron's repos suffer from the problem of depending on neutron,
+# but it not existing on pypi.
+
+# This wrapper for tox's package installer will use the existing package
+# if it exists, else use zuul-cloner if that program exists, else grab it
+# from neutron master via a hard-coded URL. That last case should only
+# happen with devs running unit tests locally.
+
+# From the tox.ini config page:
+# install_command=ARGV
+# default:
+# pip install {opts} {packages}
+
+set -x
+
+ZUUL_CLONER=/usr/zuul-env/bin/zuul-cloner
+neutron_installed=$(echo "import neutron" | python 2>/dev/null ; echo $?)
+NEUTRON_DIR=$HOME/neutron
+BRANCH_NAME=master
+
+set -e
+
+install_cmd="pip install -c$1"
+shift
+
+if [ -d "$NEUTRON_DIR" ]; then
+    echo "FOUND Neutron code at $NEUTRON_DIR - using"
+    $install_cmd -U -e $NEUTRON_DIR
+elif [ $neutron_installed -eq 0 ]; then
+    location=$(python -c "import neutron; print(neutron.__file__)")
+    echo "ALREADY INSTALLED at $location"
+elif [ -x "$ZUUL_CLONER" ]; then
+    echo "USING ZUUL CLONER to obtain Neutron code"
+    cwd=$(/bin/pwd)
+    cd /tmp
+    $ZUUL_CLONER --cache-dir \
+        /opt/git \
+        --branch $BRANCH_NAME \
+        git://git.openstack.org \
+        openstack/neutron
+    cd openstack/neutron
+    $install_cmd -e .
+    cd "$cwd"
+else
+    echo "LOCAL - Obtaining Neutron code from git.openstack.org"
+    $install_cmd -U -egit+https://git.openstack.org/openstack/neutron@$BRANCH_NAME#egg=neutron
+fi
+
+$install_cmd -U $*
+exit $?

tox.ini

@@ -5,7 +5,8 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+#install_command = pip install -U {opts} {packages}
+install_command = {toxinidir}/tools/tox_install.sh {env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning