python/exercises/practice/pov/.docs/instructions.append.md

Instructions append

Exception messages

Sometimes it is necessary to raise an exception. When you do this, you should always include a meaningful error message to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. For situations where you know that the error source will be a certain type, you can choose to raise one of the built in error types, but should still include a meaningful message.

This particular exercise requires that you use the raise statement to "throw" multiple ValueErrors if the Tree() class is passed a tree that cannot be reoriented, or a path cannot be found between a start node and an end node. The tests will only pass if you both raise the expected exception type and include the expected message with it.

Please check the tests and their expected results carefully.