Improve tools/tox_install.sh

Inspired from the tox_install script in the python-openstackclient, this
commit brings in the following improvements to glance_store's
tools/tox_install.sh:

* Do not leave temporary directory around, instead delete temporary
  directory directly after usage (change
  I939eae82dba3287fd4e4086128ebf4609a0e0770).
* Do not set ZUUL_BRANCH explicitely and remove unused if condition
  (change I0077c986a17d6bb92791474e03d1e77776e9382f).

Change-Id: I1dfa42eac22f3f9515d69146a25c4f96e55523e4

tools/tox_install.sh

@@ -15,41 +15,41 @@ CONSTRAINTS_FILE=$1
 shift
 
 install_cmd="pip install"
-if [ $CONSTRAINTS_FILE != "unconstrained" ]; then
-
-    mydir=$(mktemp -dt "$LIB_NAME-tox_install-XXXXXXX")
-    localfile=$mydir/upper-constraints.txt
-    if [[ $CONSTRAINTS_FILE != http* ]]; then
-        CONSTRAINTS_FILE=file://$CONSTRAINTS_FILE
-    fi
-    curl $CONSTRAINTS_FILE -k -o $localfile
-    install_cmd="$install_cmd -c$localfile"
-
-    if [ $requirements_installed -eq 0 ]; then
-        echo "ALREADY INSTALLED" > /tmp/tox_install.txt
-        echo "Requirements already installed; using existing package"
-    elif [ -x "$ZUUL_CLONER" ]; then
-        export ZUUL_BRANCH=${ZUUL_BRANCH-$BRANCH}
-        echo "ZUUL CLONER" > /tmp/tox_install.txt
-        pushd $mydir
-        $ZUUL_CLONER --cache-dir \
-            /opt/git \
-            --branch $BRANCH_NAME \
-            git://git.openstack.org \
-            openstack/requirements
-        cd openstack/requirements
-        $install_cmd -e .
-        popd
-    else
-        echo "PIP HARDCODE" > /tmp/tox_install.txt
-        if [ -z "$REQUIREMENTS_PIP_LOCATION" ]; then
-            REQUIREMENTS_PIP_LOCATION="git+https://git.openstack.org/openstack/requirements@$BRANCH_NAME#egg=requirements"
-        fi
-        $install_cmd -U -e ${REQUIREMENTS_PIP_LOCATION}
+mydir=$(mktemp -dt "$LIB_NAME-tox_install-XXXXXXX")
+trap "rm -rf $mydir" EXIT
+localfile=$mydir/upper-constraints.txt
+if [[ $CONSTRAINTS_FILE != http* ]]; then
+    CONSTRAINTS_FILE=file://$CONSTRAINTS_FILE
+fi
+curl $CONSTRAINTS_FILE -k -o $localfile
+install_cmd="$install_cmd -c$localfile"
+
+if [ $requirements_installed -eq 0 ]; then
+    echo "ALREADY INSTALLED" > /tmp/tox_install.txt
+    echo "Requirements already installed; using existing package"
+elif [ -x "$ZUUL_CLONER" ]; then
+    echo "ZUUL CLONER" > /tmp/tox_install.txt
+    pushd $mydir
+    $ZUUL_CLONER --cache-dir \
+        /opt/git \
+        --branch $BRANCH_NAME \
+        git://git.openstack.org \
+        openstack/requirements
+    cd openstack/requirements
+    $install_cmd -e .
+    popd
+else
+    echo "PIP HARDCODE" > /tmp/tox_install.txt
+    if [ -z "$REQUIREMENTS_PIP_LOCATION" ]; then
+        REQUIREMENTS_PIP_LOCATION="git+https://git.openstack.org/openstack/requirements@$BRANCH_NAME#egg=requirements"
     fi
-
-    edit-constraints $localfile -- $LIB_NAME "-e file://$PWD#egg=$LIB_NAME"
+    $install_cmd -U -e ${REQUIREMENTS_PIP_LOCATION}
 fi
 
+# This is the main purpose of the script: Allow local installation of
+# the current repo. It is listed in constraints file and thus any
+# install will be constrained and we need to unconstrain it.
+edit-constraints $localfile -- $LIB_NAME "-e file://$PWD#egg=$LIB_NAME"
+
 $install_cmd -U $*
 exit $?