utilities: Convert juju base into Ubuntu series

Juju 3.x replaced the `series` status key with a `base` key that
consists of Distribution type and version number.

To avoid maintenance burden we add a Launchpad module that
implements functions to look up available Ubuntu series data.

Update the `get_machine_series` helper function to determine
Ubuntu series from `base` when no `series` key is available.

Signed-off-by: Frode Nordahl <[email protected]>

zaza/utilities/juju.py

@@ -279,11 +279,26 @@ def get_machine_series(machine, model_name=None):
     :returns: Juju series
     :rtype: string
     """
-    return get_machine_status(
+    status = get_machine_status(
         machine=machine,
-        key='series',
         model_name=model_name
     )
+    try:
+        if 'series' in status:
+            return status.get('series')
+    except KeyError:
+        # libjuju will raise make the above check return KeyError when not
+        # present...
+        pass
+
+    distro, version = status.get('base', '@').split('@')
+    if not distro:
+        raise ValueError("Unable to determine distro from status: '{}'"
+                         .format(status))
+    if distro != 'ubuntu':
+        raise NotImplementedError("Series resolution not implemented for "
+                                  "distro: '{}'".format(distro))
+    return get_ubuntu_series_by_version()[version]['name']
 
 
 def get_machine_uuids_for_application(application, model_name=None):

zaza/utilities/launchpad.py

@@ -0,0 +1,50 @@
+# Copyright 2023 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+import requests
+import typing
+
+
+def get_ubuntu_series() -> typing.Dict[str,typing.List[typing.Dict[str,any]]]:
+    """Contact Launchpad API and retrieve a list of all Ubuntu releases.
+
+    Launchpad documentation for the returned data structure can be found here:
+    https://launchpad.net/+apidoc/devel.html#distribution
+    https://launchpad.net/+apidoc/devel.html#distro_series
+    """
+    r = requests.get('https://api.launchpad.net/devel/ubuntu/series')
+    return json.loads(r.text)
+
+
+def get_ubuntu_series_by_version() -> typing.Dict[str,typing.Dict[str,any]]:
+    """Get a Dict of distro series information indexed by version number.
+
+    Please refer to the `get_ubuntu_series()` function docstring for docs.
+    """
+    return {
+        entry['version']: entry
+        for entry in get_ubuntu_series().get('entries', {})
+    }
+
+
+def get_ubuntu_series_by_name() -> typing.Dict[str,typing.Dict[str,any]]:
+    """Get a Dict of distro series information indexed by version name.
+
+    Please refer to the `get_ubuntu_series()` function docstring for docs.
+    """
+    return {
+        entry['name']: entry
+        for entry in get_ubuntu_series().get('entries', {})
+    }