terraform_plan/provider_config: Send error=2 when region isn't provided

Author: refeed

src/tirith/providers/terraform_plan/handler.py

@@ -230,10 +230,20 @@ def provider_config_operator(input_data: dict, provider_inputs: dict, outputs: l
                 return
             outputs.append({"value": version_constraint, "meta": provider_config_dict})
         elif attribute_to_get == "region":
-            # TODO: The region might not be in the constant_value, it can be in a variable
+            # FIXME: The region might not be in the constant_value, it can be in a variable
+            region = provider_config_dict.get("expressions", {}).get("region", {}).get("constant_value")
+            if region is None:
+                outputs.append(
+                    {
+                        "value": ProviderError(severity_value=2),
+                        "err": f"region is not found in the provider_config (severity_value: 2)",
+                        "meta": provider_config_dict,
+                    }
+                )
+                return
             outputs.append(
                 {
-                    "value": provider_config_dict.get("expressions", {}).get("region", {}).get("constant_value"),
+                    "value": region,
                     "meta": provider_config_dict,
                 }
             )