Fix ActivityAlreadyStartedError message (#1348)

Author: dandavison

temporalio/exceptions.py

@@ -83,8 +83,8 @@ class ActivityAlreadyStartedError(FailureError):
     def __init__(
         self, activity_id: str, activity_type: str, *, run_id: str | None = None
     ) -> None:
-        """Initialize a workflow already started error."""
-        super().__init__("Workflow execution already started")
+        """Initialize an activity already started error."""
+        super().__init__("Activity execution already started")
         self.activity_id = activity_id
         self.activity_type = activity_type
         self.run_id = run_id

tests/test_activity.py

@@ -847,6 +847,9 @@ async def test_id_conflict_policy_fail(client: Client, env: WorkflowEnvironment)
             id_conflict_policy=ActivityIDConflictPolicy.FAIL,
         )
     assert err.value.activity_id == activity_id
+    assert "Activity" in str(
+        err.value
+    ), f"Expected 'Activity' in error message, got: {err.value}"
 
 
 async def test_id_conflict_policy_use_existing(