refactored and added tests to policy

rasa/core/policies/flows/flow_exceptions.py

@@ -0,0 +1,31 @@
+from rasa.dialogue_understanding.stack.dialogue_stack import DialogueStack
+from rasa.shared.exceptions import RasaException
+
+
+class FlowException(RasaException):
+    """Exception that is raised when there is a problem with a flow."""
+
+    pass
+
+
+class FlowCircuitBreakerTrippedException(FlowException):
+    """Exception that is raised when the flow circuit breaker tripped.
+
+    The circuit breaker gets tripped when a flow seems to be stuck in
+    executing steps and does not make any progress."""
+
+    def __init__(
+        self, dialogue_stack: DialogueStack, number_of_steps_taken: int
+    ) -> None:
+        """Creates a `FlowCircuitBreakerTrippedException`.
+
+        Args:
+            dialogue_stack: The dialogue stack.
+            number_of_steps_taken: The number of steps that were taken.
+        """
+        super().__init__(
+            f"Flow circuit breaker tripped after {number_of_steps_taken} steps. "
+            "There appears to be an infinite loop in the flows."
+        )
+        self.dialogue_stack = dialogue_stack
+        self.number_of_steps_taken = number_of_steps_taken