FunctionalCommand: Assert lifecycle functions are callable

Author: auscompgeek

commands2/functionalcommand.py

@@ -31,6 +31,11 @@ def __init__(
         :param requirements: the subsystems required by this command"""
         super().__init__()
 
+        assert callable(onInit)
+        assert callable(onExecute)
+        assert callable(onEnd)
+        assert callable(isFinished)
+
         self._onInit = onInit
         self._onExecute = onExecute
         self._onEnd = onEnd