Add python3.6 pip support

Since pip v22, python3.6 is not supported (the minimum version is
python3.7). This patch adds the reference for the pip3.6 URL to be
used instead of the default one.

Closes-Bug: #1959600
Change-Id: Iab2c391d5388461fe9e9037cee81884ce8032e72

Author: ralonsoh

tools/install_pip.sh

@@ -38,7 +38,7 @@ FILES=$TOP_DIR/files
 # [1] https://opendev.org/openstack/project-config/src/branch/master/nodepool/elements/cache-devstack/source-repository-pip
 
 PIP_GET_PIP_URL=${PIP_GET_PIP_URL:-"https://bootstrap.pypa.io/get-pip.py"}
-LOCAL_PIP="$FILES/$(basename $PIP_GET_PIP_URL)"
+PIP_GET_PIP36_URL=${PIP_GET_PIP36_URL:-"https://bootstrap.pypa.io/pip/3.6/get-pip.py"}
 
 GetDistro
 echo "Distro: $DISTRO"
@@ -57,12 +57,21 @@ function get_versions {
 
 
 function install_get_pip {
+    if [[ "$PYTHON3_VERSION" = "3.6" ]]; then
+        _pip_url=$PIP_GET_PIP36_URL
+        _local_pip="$FILES/$(basename $_pip_url)-py36"
+    else
+        _pip_url=$PIP_GET_PIP_URL
+        _local_pip="$FILES/$(basename $_pip_url)"
+    fi
+
+
     # If get-pip.py isn't python, delete it. This was probably an
     # outage on the server.
-    if [[ -r $LOCAL_PIP ]]; then
-        if ! head -1 $LOCAL_PIP | grep -q '#!/usr/bin/env python'; then
-            echo "WARNING: Corrupt $LOCAL_PIP found removing"
-            rm $LOCAL_PIP
+    if [[ -r $_local_pip ]]; then
+        if ! head -1 $_local_pip | grep -q '#!/usr/bin/env python'; then
+            echo "WARNING: Corrupt $_local_pip found removing"
+            rm $_local_pip
         fi
     fi
 
@@ -76,20 +85,20 @@ function install_get_pip {
     # Thus we use curl's "-z" feature to always check the modified
     # since and only download if a new version is out -- but only if
     # it seems we downloaded the file originally.
-    if [[ ! -r $LOCAL_PIP || -r $LOCAL_PIP.downloaded ]]; then
+    if [[ ! -r $_local_pip || -r $_local_pip.downloaded ]]; then
         # only test freshness if LOCAL_PIP is actually there,
         # otherwise we generate a scary warning.
         local timecond=""
-        if [[ -r $LOCAL_PIP ]]; then
-            timecond="-z $LOCAL_PIP"
+        if [[ -r $_local_pip ]]; then
+            timecond="-z $_local_pip"
         fi
 
         curl -f --retry 6 --retry-delay 5 \
-            $timecond -o $LOCAL_PIP $PIP_GET_PIP_URL || \
+            $timecond -o $_local_pip $_pip_url || \
             die $LINENO "Download of get-pip.py failed"
-        touch $LOCAL_PIP.downloaded
+        touch $_local_pip.downloaded
     fi
-    sudo -H -E python${PYTHON3_VERSION} $LOCAL_PIP
+    sudo -H -E python${PYTHON3_VERSION} $_local_pip
 }