Fix style issues and datetime deprecation warning in safeguards

Author: ShantingLiu

src/azure-cli/azure/cli/command_modules/acs/custom.py

@@ -44,7 +44,6 @@
 import yaml
 from azure.cli.command_modules.acs._client_factory import (
     cf_agent_pools,
-    get_container_service_client,
 )
 from azure.cli.command_modules.acs._consts import (
     ADDONS,
@@ -197,35 +196,38 @@ def _build_arguments_schema(cls, *args, **kwargs):
 class AKSSafeguardsCreateCustom(Create):
 
     def pre_operations(self):
-        from azure.cli.core.azclierror import ClientRequestError
         from azure.cli.core.util import send_raw_request
-        
+
         # Validate and set managed cluster argument first
         _validate_and_set_managed_cluster_argument(self.ctx)
-        
+
         # Check if Deployment Safeguards already exists
         resource_group_name = self.ctx.args.resource_group
         cluster_name = self.ctx.args.cluster_name
         subscription_id = self.ctx.subscription_id
-        
+
         # Construct the URL to check if safeguards already exists
-        safeguards_url = f"https://management.azure.com/subscriptions/{subscription_id}/resourceGroups/{resource_group_name}/providers/Microsoft.ContainerService/managedClusters/{cluster_name}/providers/Microsoft.ContainerService/deploymentSafeguards/default?api-version=2025-05-02-preview"
-        
+        safeguards_url = (
+            "https://management.azure.com/subscriptions/{}/resourceGroups/{}/providers/"
+            "Microsoft.ContainerService/managedClusters/{}/providers/Microsoft.ContainerService/"
+            "deploymentSafeguards/default?api-version=2025-05-02-preview"
+        ).format(subscription_id, resource_group_name, cluster_name)
+
         # Check if resource already exists
         resource_exists = False
         try:
             response = send_raw_request(self.ctx.cli_ctx, "GET", safeguards_url)
             if response.status_code == 200:
                 resource_exists = True
-        except Exception:
+        except Exception:  # pylint: disable=broad-exception-caught
             # 404 or any error means resource doesn't exist
             pass
-        
+
         if resource_exists:
             raise ClientRequestError(
-                f"Deployment Safeguards instance already exists for this cluster. "
-                f"Please use 'az aks safeguards update' to modify the configuration, "
-                f"or 'az aks safeguards delete' to remove it before creating a new one."
+                "Deployment Safeguards instance already exists for this cluster. "
+                "Please use 'az aks safeguards update' to modify the configuration, "
+                "or 'az aks safeguards delete' to remove it before creating a new one."
             )
 
     @classmethod
@@ -1384,7 +1386,7 @@ def _update_upgrade_settings(cmd, instance,
                     f"{upgrade_override_until} is not a valid datatime format."
                 )
         elif force_upgrade:
-            default_extended_until = datetime.datetime.utcnow() + datetime.timedelta(days=3)
+            default_extended_until = datetime.datetime.now(datetime.UTC) + datetime.timedelta(days=3)
             if existing_until is None or existing_until.timestamp() < default_extended_until.timestamp():
                 instance.upgrade_settings.override_settings.until = default_extended_until
     return instance