Python Exception Context

import traceback


class MyException(Exception):
    def __init__(self, message, cutom):
        super().__init__(message)
        self.custom = cutom


test = [0, 1, 2]


def do():
    try:
        print(test[3])
    except Exception as err:
        print(repr(err))
        print("------------")
        raise MyException(repr(err), "test") from err


def main():
    try:
        do()
    except BaseException as err:
        print(repr(err))
        print("------------")
        print(traceback.format_exc())
        print("------------")
        print(err.custom)


main()

IndexError('list index out of range')
------------
MyException("IndexError('list index out of range')")
------------
Traceback (most recent call last):
  File "/Users/zztkm/dev/sandbox/pydev/exception-test/main.py", line 15, in do
    print(test[3])
IndexError: list index out of range

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/zztkm/dev/sandbox/pydev/exception-test/main.py", line 24, in main
    do()
  File "/Users/zztkm/dev/sandbox/pydev/exception-test/main.py", line 19, in do
    raise MyException(repr(err), "test") from err
MyException: IndexError('list index out of range')

------------
test