Mark support for py38

in 'wallaby' cycle, we should test py38 by default.
Also support tox test on py36 and py38 as that's what
our check job verify on.
ref:
  https://governance.openstack.org/tc/reference/runtimes/victoria.html

Change-Id: I349d80cb1b963bdb30e374994f7c18352f918e3b

heat_cfntools/cfntools/cfn_helper.py

@@ -311,7 +311,7 @@ class RpmHelper(object):
         Arguments:
             pkg -- A package name
         """
-        cmd = "rpm -q --queryformat '%{VERSION}-%{RELEASE}' %s" % pkg
+        cmd = "rpm -q --queryformat '%%{VERSION}-%%{RELEASE}' %s" % pkg
         command = CommandRunner(cmd).run()
         return command.stdout
 

setup.cfg

@@ -17,6 +17,7 @@ classifier =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
 
 [files]
 packages =

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py37,pep8
+envlist = py36,py37,py38,pep8
 ignore_basepython_conflict = true
 
 [testenv]