From 4324f4ecd99f3cc50dea585bc8b5a680327e54bc Mon Sep 17 00:00:00 2001
From: Sean Dague <sean@dague.net>
Date: Thu, 14 Sep 2017 12:59:25 -0600
Subject: [PATCH] Fix devstack python detection if python3 is missing

On platforms without python3 installed devstack fails the python
version check. This does it more gracefully.

Change-Id: I4d79a41eb2d66852ab1a1aa8bd383f8e3e89cdc0
---
 functions-common | 5 ++++-
 stackrc          | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/functions-common b/functions-common
index deebdec249..b9bf0c9788 100644
--- a/functions-common
+++ b/functions-common
@@ -2080,7 +2080,10 @@ function is_provider_network {
 function _get_python_version {
     local interp=$1
     local version
-    version=$($interp -c 'import sys; print("%s.%s" % sys.version_info[0:2])')
+    # disable erroring out here, otherwise if python 3 doesn't exist we fail hard.
+    if [[ -x $(which $interp) ]]; then
+        version=$($interp -c 'import sys; print("%s.%s" % sys.version_info[0:2])')
+    fi
     echo ${version}
 }
 
diff --git a/stackrc b/stackrc
index 92a939f164..d60e186448 100644
--- a/stackrc
+++ b/stackrc
@@ -131,11 +131,11 @@ export DISABLED_PYTHON3_PACKAGES=""
 # version of Python 3 to this variable will install the app using that
 # version of the interpreter instead of 2.7.
 _DEFAULT_PYTHON3_VERSION="$(_get_python_version python3)"
-export PYTHON3_VERSION=${PYTHON3_VERSION:-${_DEFAULT_PYTHON3_VERSION}}
+export PYTHON3_VERSION=${PYTHON3_VERSION:-${_DEFAULT_PYTHON3_VERSION:-3.5}}
 
 # Just to be more explicit on the Python 2 version to use.
 _DEFAULT_PYTHON2_VERSION="$(_get_python_version python2)"
-export PYTHON2_VERSION=${PYTHON2_VERSION:-${_DEFAULT_PYTHON2_VERSION}}
+export PYTHON2_VERSION=${PYTHON2_VERSION:-${_DEFAULT_PYTHON2_VERSION:-2.7}}
 
 # allow local overrides of env variables, including repo config
 if [[ -f $RC_DIR/localrc ]]; then