Address python3 string issues with subprocess

This patch updates our Popen call to enable
newlines for calls that we parse or consume the output for.
Without universal_newlines=True, the output is treated as bytes
under python3 which leads to issues later where we are using it as
strings.

See https://docs.python.org/3/glossary.html#term-universal-newlines

Story: 2006796
Task:  42712

Signed-off-by: Charles Short <charles.short@windriver.com>
Change-Id: Ib9f6e9e9bb6ba465993f0ffa4579e86c52716190

python-k8sapp-openstack/k8sapp_openstack/k8sapp_openstack/helm/openstack.py

@@ -106,7 +106,8 @@ class OpenstackBaseHelm(base.BaseHelm):
             if pw_format == common.PASSWORD_FORMAT_CEPH:
                 try:
                     cmd = ['ceph-authtool', '--gen-print-key']
-                    password = subprocess.check_output(cmd).strip()
+                    password = subprocess.check_output(cmd,
+                            universal_newlines=True).strip()
                 except subprocess.CalledProcessError:
                     raise exception.SysinvException(
                         'Failed to generate ceph key')