test: fix blocked status and blocked status tests

flake.nix

@@ -0,0 +1,37 @@
+{
+  description = "juju controller charm shell";
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-24.05";
+  };
+
+  outputs = { self, nixpkgs, ... } @ inputs:
+    let
+      forAllSystems = inputs.nixpkgs.lib.genAttrs [
+        "aarch64-linux"
+        "x86_64-linux"
+        "aarch64-darwin"
+      ];
+    in
+    {
+      devShells = forAllSystems (system: {
+        default =
+          let
+            pkgs = nixpkgs.legacyPackages.${system};
+          in
+          pkgs.mkShell {
+            name = "juju-controller-charm";
+            # Enable experimental features without having to specify the argument
+            NIX_CONFIG = "experimental-features = nix-command flakes";
+            nativeBuildInputs = with pkgs; [
+              coreutils
+              findutils
+              zsh
+              python312
+            ];
+            shellHook = ''
+              exec zsh
+            '';
+          };
+      });
+    };
+}

src/charm.py

@@ -131,7 +131,7 @@ def _on_metrics_endpoint_relation_created(self, event: RelationJoinedEvent):
         except AgentConfException as e:
             logger.error('cannot read controller API port from agent configuration: %s', e)
             self.unit.status = BlockedStatus(
-                f"can't read controller API port from agent.conf: {e}")
+                f"cannot read controller API port from agent configuration: {e}")
             return
 
         metrics_endpoint = MetricsEndpointProvider(

tests/test_charm.py

@@ -140,7 +140,8 @@ def test_apiaddresses_missing_status(self, *_):
         harness.add_relation('metrics-endpoint', 'prometheus-k8s')
         harness.evaluate_status()
         self.assertEqual(harness.charm.unit.status, BlockedStatus(
-            "can't read controller API port from agent.conf: agent.conf key 'apiaddresses' missing"
+            "cannot read controller API port from agent configuration: "
+            "agent.conf key 'apiaddresses' missing"
         ))
 
     @patch("builtins.open", new_callable=mock_open, read_data=agent_conf_ipv4)