Customize assertion message in test [duplicate]

This question already has an answer here:

• Customize AssertionError in Python 3 answers

I want to customize my error in unittest. I have code

from exceptions import AssertionError


class AssertionError(AssertionError):
    def __str__(self):
        return super(AssertionError, self).__str__() + " SOME TEXT"

but during test execution I don't see my text 'SOME TEXT'.

class TestCase(unittest.TestCase):
    def test1111(self):
        self.assertTrue(False, "FAIL")

I expected to see:

AssertionError: FAIL SOME TEXT

Overriding works for assert statement but doesn't work in test.