Pytest Change the text of the exception

---

examples/pytest/fib3/fibonacci.py

def fib(n):
    if n < 1:
        raise ValueError(f'Invalid parameter was given {n}')
    a, b = 1, 1
    for _ in range(1, n):
        a, b = b, a+b
    return a

examples/pytest/fib3/test_fibonacci.py

import pytest
from fibonacci import fib

def test_fib():
    assert fib(10) == 55

def test_fib_negative():
    with pytest.raises(Exception) as err:
        fib(-1)
    assert err.type == ValueError
    assert str(err.value) == 'Invalid parameter -1'

def test_fib_negative_again():
    with pytest.raises(ValueError) as err:
        fib(-1)
    assert str(err.value) == 'Invalid parameter -1'

============================= test session starts ==============================
platform linux -- Python 3.8.6, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/gabor/work/slides/python/examples/pytest/fib3
plugins: flake8-1.0.6, dash-1.17.0
collected 3 items

test_fibonacci.py .FF                                                    [100%]

=================================== FAILURES ===================================
______________________________ test_fib_negative _______________________________

    def test_fib_negative():
        with pytest.raises(Exception) as err:
            fib(-1)
        assert err.type == ValueError
>       assert str(err.value) == 'Invalid parameter -1'
E       AssertionError: assert 'Invalid para... was given -1' == 'Invalid parameter -1'
E         - Invalid parameter -1
E         + Invalid parameter was given -1
E         ?                   ++++++++++

test_fibonacci.py:11: AssertionError
___________________________ test_fib_negative_again ____________________________

    def test_fib_negative_again():
        with pytest.raises(ValueError) as err:
            fib(-1)
>       assert str(err.value) == 'Invalid parameter -1'
E       AssertionError: assert 'Invalid para... was given -1' == 'Invalid parameter -1'
E         - Invalid parameter -1
E         + Invalid parameter was given -1
E         ?                   ++++++++++

test_fibonacci.py:16: AssertionError
=========================== short test summary info ============================
FAILED test_fibonacci.py::test_fib_negative - AssertionError: assert 'Invalid...
FAILED test_fibonacci.py::test_fib_negative_again - AssertionError: assert 'I...
========================= 2 failed, 1 passed in 0.03s ==========================