Refactor cable tracing logic

netbox/dcim/exceptions.py

@@ -3,3 +3,12 @@ class LoopDetected(Exception):
     A loop has been detected while tracing a cable path.
     """
     pass
+
+
+class CableTraceSplit(Exception):
+    """
+    A cable trace cannot be completed because a RearPort maps to multiple FrontPorts and
+    we don't know which one to follow.
+    """
+    def __init__(self, termination, *args, **kwargs):
+        self.termination = termination