Install Python3.6 for Ubuntu images

Add Python3.6 version to be used by dcaegen2
project.

Change-Id: Ie6a1afde8a4697f094a862bfd0870fc5a844bf47
Issue-ID: CIMAN-108
Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
diff --git a/packer/provision/docker.sh b/packer/provision/docker.sh
index 593b5c7..325e328 100644
--- a/packer/provision/docker.sh
+++ b/packer/provision/docker.sh
@@ -32,6 +32,11 @@
 ubuntu_systems() {
     # Assumes that python is already installed by basebuild
 
+    # Install Python3.6
+    sudo add-apt-repository -y ppa:jonathonf/python-3.6
+    sudo apt-get update
+    sudo apt-get install -y python3.6
+
     # Install dependencies for robotframework and robotframework-sshlibrary
     apt install -y unzip sshuttle netcat libffi-dev libssl-dev
     wget https://github.com/mozilla/geckodriver/releases/download/v0.18.0/geckodriver-v0.18.0-linux64.tar.gz