Merge ~ack/maas:1948965-lxd-check-caps-on-compose into maas:master

[Alberto Donato]

LP:1948965 check LXD server capabilities on VM compose

[Adam Collard (adam-collard)]

review: Approve

[MAAS Lander (maas-lander)]

LANDING
-b 1948965-lxd-check-caps-on-compose lp:~ack/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: FAILED BUILD
LOG: http://maas-ci.internal:8080/job/maas/job/branch-tester/11398/consoleText

diff --git a/src/provisioningserver/drivers/pod/lxd.py b/src/provisioningserver/drivers/pod/lxd.py
index c663254..2ef7f8c 100644
--- a/src/provisioningserver/drivers/pod/lxd.py
+++ b/src/provisioningserver/drivers/pod/lxd.py
@@ -437,6 +437,8 @@ class LXDPodDriver(PodDriver):
     def compose(self, pod_id: int, context: dict, request: RequestedMachine):
         """Compose a virtual machine."""
         with self._get_client(pod_id, context) as client:
+            self._check_required_extensions(client)
+
             storage_pools = client.storage_pools.all()
             default_storage_pool = context.get(
                 "default_storage_pool_id", context.get("default_storage_pool")
diff --git a/src/provisioningserver/drivers/pod/tests/test_lxd.py b/src/provisioningserver/drivers/pod/tests/test_lxd.py
index b88cdba..c74af1f 100644
--- a/src/provisioningserver/drivers/pod/tests/test_lxd.py
+++ b/src/provisioningserver/drivers/pod/tests/test_lxd.py
@@ -1452,6 +1452,18 @@ class TestLXDPodDriver(MAASTestCase):
             yield self.driver.compose(None, self.make_context(), request)
 
     @inlineCallbacks
+    def test_compose_checks_required_extensions(self):
+        self.fake_lxd.host_info["api_extensions"].remove("projects")
+        error_msg = (
+            "Please upgrade your LXD host to 4.16 or higher "
+            "to support the following extensions: projects"
+        )
+        with ExpectedException(lxd_module.LXDPodError, error_msg):
+            yield self.driver.compose(
+                None, self.make_context(), make_requested_machine()
+            )
+
+    @inlineCallbacks
     def test_compose_multiple_disks(self):
         pod_id = factory.make_name("pod_id")
         request = make_requested_machine(num_disks=2)