[ops-sunbeam] Update harness private paths

ops 2.17 officially deprecated harness and moved some of the internal
paths (that we're not supposed to use, but we do). Update these paths,
but we need to move off harness at some point.

Change-Id: If3921e4f8bdd2c5973e30793267308ac9fa0d951
Signed-off-by: Guillaume Boutry <guillaume.boutry@canonical.com>

ops-sunbeam/ops_sunbeam/test_utils.py

@@ -52,13 +52,15 @@ from ops import (
     framework,
     model,
 )
+from ops._private.harness import (
+    _TestingModelBackend,
+    _TestingPebbleClient,
+)
 from ops.jujucontext import (
     _JujuContext,
 )
 from ops.testing import (
     Harness,
-    _TestingModelBackend,
-    _TestingPebbleClient,
 )
 
 TEST_CA = """-----BEGIN CERTIFICATE-----

test-requirements.txt

@@ -2,14 +2,13 @@ stestr
 coverage
 
 tenacity                   # ops-sunbeam
-ops                        # all charms
+ops[testing]>=2.17.0       # all charms, private paths have moved
 lightkube                  # almost all charms
 pwgen                      # keystone-k8s
 python-keystoneclient      # keystone-k8s
 cryptography               # neutron-k8s
 jsonschema                 # neutron-k8s
 pytest-interface-tester    # barbican-k8s
-ops-scenario<7             # barbican-k8s, see bug https://github.com/canonical/pytest-interface-tester/issues/23
 pydantic                   # traefik-k8s ingress lib
 requests                   # cinder-ceph-k8s
 netifaces                  # cinder-ceph-k8s