pytest execution for set equality

foo.py:

```
def test_a():
    assert set([1, 2, 3]) == set([2, 3])
```


$ pytest foo.py 
============================= test session starts ==============================
platform linux -- Python 3.6.9, pytest-4.5.0, py-1.8.0, pluggy-0.11.0
rootdir: /home/math/Desktop
plugins: pylint-0.14.0, mccabe-0.1, flake8-1.0.4, env-0.6.2, cov-2.7.1, black-0.3.7
collected 1 item                                                               

foo.py F                                                                 [100%]

=================================== FAILURES ===================================
____________________________________ test_a ____________________________________

    def test_a():
>       assert set([1, 2, 3]) == set([2, 3])
E       assert {1, 2, 3} == {2, 3}
E         Extra items in the left set:
E         1
E         Use -v to get the full diff

foo.py:2: AssertionError
=========================== 1 failed in 0.04 seconds ===========================