diff --git a/tools/pip_install.sh b/tools/pip_install.sh
deleted file mode 100755
index c7568eb9..00000000
--- a/tools/pip_install.sh
+++ /dev/null
@@ -1,52 +0,0 @@
-#!/bin/sh
-
-# This script is borrowed from Sahara who borrowed from neutron-* repos.
-
-# Many of horizon's repos suffer from the problem of depending on horizon,
-# 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 horizon 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}
-
-ZUUL_CLONER=/usr/zuul-env/bin/zuul-cloner
-BRANCH_NAME=master
-horizon_installed=$(echo "import horizon" | python 2>/dev/null ; echo $?)
-
-set -e
-
-install_cmd="pip install $1"
-shift
-
-if [ $horizon_installed -eq 0 ]; then
-    echo "ALREADY INSTALLED" > /tmp/tox_install.txt
-    echo "Horizon already installed; using existing package"
-elif [ -x "$ZUUL_CLONER" ]; then
-    export ZUUL_BRANCH=${ZUUL_BRANCH-$BRANCH}
-    echo "ZUUL CLONER" > /tmp/tox_install.txt
-    cwd=$(/bin/pwd)
-    cd /tmp
-    $ZUUL_CLONER --cache-dir \
-        /opt/git \
-        --branch $BRANCH_NAME \
-        git://git.openstack.org \
-        openstack/horizon
-    cd openstack/horizon
-    $install_cmd -e .
-    cd "$cwd"
-else
-    echo "PIP HARDCODE" > /tmp/tox_install.txt
-    if [ -z "$HORIZON_PIP_LOCATION" ]; then
-        HORIZON_PIP_LOCATION="git+https://git.openstack.org/openstack/horizon@$BRANCH_NAME#egg=horizon"
-    fi
-    $install_cmd -U -e ${HORIZON_PIP_LOCATION}
-fi
-
-$install_cmd -U $*
-exit $?
diff --git a/tools/tox_install.sh b/tools/tox_install.sh
new file mode 100755
index 00000000..ebb83154
--- /dev/null
+++ b/tools/tox_install.sh
@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+
+# Many of horizon's repos suffer from the problem of depending on horizon,
+# but it not existing on pypi.
+
+# This wrapper for tox's package installer will use the existing package
+# if it exists, else use zuul-cloner if that program exists, else grab it
+# from horizon master via a hard-coded URL. That last case should only
+# happen with devs running unit tests locally.
+
+# From the tox.ini config page:
+# install_command=ARGV
+# default:
+# pip install {opts} {packages}
+
+ZUUL_CLONER=/usr/zuul-env/bin/zuul-cloner
+BRANCH_NAME=master
+GIT_BASE=${GIT_BASE:-https://git.openstack.org/}
+
+install_project() {
+    local project=$1
+    local branch=${2:-$BRANCH_NAME}
+    local module_name=${project//-/_}
+
+    set +e
+    project_installed=$(echo "import $module_name" | python 2>/dev/null ; echo $?)
+    set -e
+
+    if [ $project_installed -eq 0 ]; then
+        echo "ALREADY INSTALLED" > /tmp/tox_install.txt
+        echo "$project already installed; using existing package"
+    elif [ -x "$ZUUL_CLONER" ]; then
+        echo "ZUUL CLONER" > /tmp/tox_install.txt
+        # Make this relative to current working directory so that
+        # git clean can remove it. We cannot remove the directory directly
+        # since it is referenced after $install_cmd -e
+        mkdir -p .tmp
+        PROJECT_DIR=$(/bin/mktemp -d -p $(pwd)/.tmp)
+        pushd $PROJECT_DIR
+        $ZUUL_CLONER --cache-dir \
+            /opt/git \
+            --branch $branch \
+            http://git.openstack.org \
+            openstack/$project
+        cd openstack/$project
+        $install_cmd -e .
+        popd
+    else
+        echo "PIP HARDCODE" > /tmp/tox_install.txt
+        local GIT_REPO="$GIT_BASE/openstack/$project"
+        SRC_DIR="$VIRTUAL_ENV/src/$project"
+        git clone --depth 1 --branch $branch $GIT_REPO $SRC_DIR
+        $install_cmd -U -e $SRC_DIR
+    fi
+}
+
+set -e
+
+install_cmd="pip install -c$1"
+shift
+
+install_project horizon
+
+$install_cmd -U $*
+exit $?
diff --git a/tox.ini b/tox.ini
index c5bec30b..ddfbc779 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,8 +5,8 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = {toxinidir}/tools/pip_install.sh \
-                  -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} \
+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}
@@ -102,7 +102,7 @@ commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasen
 local-check-factory = horizon.hacking.checks.factory
 
 [flake8]
-exclude = .venv,.git,.tox,dist,*lib/python*,*egg,build,panel_template,dash_template,local_settings.py,*/local/*,*/test/test_plugins/*,.ropeproject,node_modules
+exclude = .venv,.git,.tox,dist,*lib/python*,*egg,build,panel_template,dash_template,local_settings.py,*/local/*,*/test/test_plugins/*,.ropeproject,node_modules,.tmp
 max-complexity = 20
 import-order-style = pep8