integration_tests: bump pycloudlib dependency (#846)

The latest pycloudlib now launches official Ubuntu cloud images for
xenial, meaning that `lxc exec` no longer works against them.  This
commit includes handling for tests which are affected by this change;
further details and reasoning in the included comment.

2 files changed, 22 insertions, 1 deletions

diff --git a/integration-requirements.txt b/integration-requirements.txt
index fb4c3ba1..95891356 100644
--- a/integration-requirements.txt
+++ b/integration-requirements.txt
@@ -1,5 +1,5 @@
 # PyPI requirements for cloud-init integration testing
 # https://cloudinit.readthedocs.io/en/latest/topics/integration_tests.html
 #
-pycloudlib @ git+https://github.com/canonical/pycloudlib.git@5975c7e60be4a1e95814909a35592634cc145938
+pycloudlib @ git+https://github.com/canonical/pycloudlib.git@96b146ee1beb99b8e44e36525e18a9a20e00c3f2
 pytest
diff --git a/tests/integration_tests/conftest.py b/tests/integration_tests/conftest.py
index 0b93c94f..6f4ce8d3 100644
--- a/tests/integration_tests/conftest.py
+++ b/tests/integration_tests/conftest.py
@@ -45,6 +45,17 @@ os_list = ["ubuntu"]
 
 session_start_time = datetime.datetime.now().strftime('%y%m%d%H%M%S')
 
+XENIAL_LXD_VM_EXEC_MSG = """\
+The default xenial images do not support `exec` for LXD VMs.
+
+Specify an image known to work using:
+
+    OS_IMAGE=<image id>::ubuntu::xenial
+
+You can re-run specifically tests that require this by passing `-m
+lxd_use_exec` to pytest.
+"""
+
 
 def pytest_runtest_setup(item):
     """Skip tests on unsupported clouds.
@@ -216,6 +227,16 @@ def _client(request, fixture_utils, session_cloud: IntegrationCloud):
     if lxd_use_exec is not None:
         if not isinstance(session_cloud, _LxdIntegrationCloud):
             pytest.skip("lxd_use_exec requires LXD")
+        if isinstance(session_cloud, LxdVmCloud):
+            image_spec = ImageSpecification.from_os_image()
+            if image_spec.release == image_spec.image_id == "xenial":
+                # Why fail instead of skip?  We expect that skipped tests will
+                # be run in a different one of our usual battery of test runs
+                # (e.g. LXD-only tests are skipped on EC2 but will run in our
+                # normal LXD test runs).  This is not true of this test: it
+                # can't run in our usual xenial LXD VM test run, and it may not
+                # run anywhere else.  A failure flags up this discrepancy.
+                pytest.fail(XENIAL_LXD_VM_EXEC_MSG)
         launch_kwargs["execute_via_ssh"] = False
 
     with session_cloud.launch(