Handle exception in create-missing-principals because there are no UC roles (#4373)

## Changes
Handle exception in `create-missing-principals` because there are no UC
roles, exit gracefully with an informative message instead of failing.

### Linked issues
Resolves #4372

Author: pritishpai

src/databricks/labs/ucx/aws/access.py

@@ -9,7 +9,7 @@
 from databricks.labs.blueprint.parallel import Threads
 from databricks.labs.blueprint.tui import Prompts
 from databricks.sdk import WorkspaceClient
-from databricks.sdk.errors import NotFound, ResourceDoesNotExist, PermissionDenied
+from databricks.sdk.errors import NotFound, PermissionDenied
 from databricks.sdk.service.catalog import Privilege
 from databricks.sdk.service.compute import Policy
 from databricks.sdk.service.sql import SetWorkspaceWarehouseConfigRequestSecurityPolicy
@@ -155,7 +155,7 @@ def save_uc_compatible_roles(self):
     def load_uc_compatible_roles(self, *, resource_type: AWSResourceType | None = None) -> list[AWSRoleAction]:
         try:
             role_actions = self._installation.load(list[AWSRoleAction], filename=self.UC_ROLES_FILE_NAME)
-        except ResourceDoesNotExist:
+        except NotFound:
             self.save_uc_compatible_roles()
             role_actions = self._installation.load(list[AWSRoleAction], filename=self.UC_ROLES_FILE_NAME)
         if resource_type:
@@ -236,7 +236,11 @@ def _get_role_access_task(self, arn: str, role_name: str):
 
     def _identify_missing_paths(self):
         external_locations = self._locations.external_locations_with_root()
-        compatible_roles = self.load_uc_compatible_roles()
+        try:
+            compatible_roles = self.load_uc_compatible_roles()
+        except NotFound:
+            logger.warning(f"{self.UC_ROLES_FILE_NAME} not found.")
+            compatible_roles = []
         missing_paths = set()
         for external_location in external_locations:
             matching_role = False

tests/unit/aws/test_access.py

@@ -132,7 +132,7 @@ def installation_multiple_roles():
 
 @pytest.fixture
 def installation_no_roles():
-    return MockInstallation(DEFAULT_CONFIG | {"uc_roles_access.csv": []})
+    return MockInstallation(DEFAULT_CONFIG | {})
 
 
 @pytest.fixture