Handle non-standard version strings coming from api

juju/client/connector.py

@@ -4,7 +4,7 @@
 import copy
 import logging
 
-from packaging import version
+from packaging import version, InvalidVersion
 
 import macaroonbakery.httpbakery as httpbakery
 
@@ -13,7 +13,7 @@
 from juju.client.gocookies import GoCookieJar, go_to_py_cookie
 from juju.client.jujudata import API_ENDPOINTS_KEY, FileJujuData
 from juju.client.proxy.factory import proxy_from_config
-from juju.errors import JujuConnectionError, JujuError
+from juju.errors import JujuConnectionError, JujuError, JujuUnknownVersion
 from juju.version import CLIENT_VERSION
 
 log = logging.getLogger("connector")
@@ -88,7 +88,17 @@ async def connect(self, **kwargs):
             self._connection = await Connection.connect(**kwargs)
 
         # Check if we support the target controller
-        juju_server_version = version.parse(self._connection.info["server-version"])
+        server_version = self._connection.info["server-version"]
+        try:
+            juju_server_version = version.parse(server_version)
+        except InvalidVersion as err:
+            # We're only interested in the major version, so
+            # we attempt to clean up versions such as 3.4-rc1.2 as just 3.4
+            if '-' not in server_version:
+                raise JujuUnknownVersion(err)
+            juju_server_version = version.parse(server_version.split('-')[0])
+
+        # CLIENT_VERSION statically comes from the VERSION file in the repo
         client_version = version.parse(CLIENT_VERSION)
 
         if juju_server_version.major != client_version.major:

juju/errors.py

@@ -137,3 +137,7 @@ class AbstractMethodError(Exception):
 
 class PylibjujuError(JujuError):
     pass
+
+
+class JujuUnknownVersion(PylibjujuError):
+    pass