py3: Switch to using Python 3 for rocky or later

Switch package install to Python 3 for OpenStack Rocky or later.

Depends-On: I17a93524fb7ec134b4a3a61cd0e86977daf49c4e

Change-Id: Ia63ee8ced1299eccd84d4d07d5272234e8737e17

src/lib/charm/openstack/aodh.py

@@ -150,6 +150,30 @@ class AodhCharmOcata(AodhCharm):
         # no need to restart aodh-api in ocata and onwards
 
 
+class AodhCharmRocky(AodhCharmOcata):
+
+    release = 'rocky'
+
+    # Switch to Python 3 for Rocky onwards
+    packages = [
+        'aodh-api',
+        'aodh-evaluator',
+        'aodh-expirer',
+        'aodh-notifier',
+        'aodh-listener',
+        'python3-aodh',
+        'libapache2-mod-wsgi-py3',
+        'python-apt',  # NOTE: workaround for hacluster suboridinate
+    ]
+
+    purge_packages = [
+        'python-aodh',
+        'python-memcache',
+    ]
+
+    python_version = 3
+
+
 def install():
     """Use the singleton from the AodhCharm to install the packages on the
     unit

src/tox.ini

@@ -35,7 +35,7 @@ commands =
 # Run a specific test as an Amulet smoke test (expected to always pass)
 basepython = python2.7
 commands =
-    bundletester -vl DEBUG -r json -o func-results.json gate-basic-bionic-queens --no-destroy
+    bundletester -vl DEBUG -r json -o func-results.json gate-basic-bionic-rocky --no-destroy
 
 [testenv:func27-dfs]
 # Run all deploy-from-source tests which are +x (may not always pass!)