Remove a lot of test references to Python 2/3.5

test/completion/pytest.py

@@ -1,4 +1,3 @@
-# python > 2.7
 import pytest
 from pytest import fixture
 
@@ -130,8 +129,6 @@ def test_p(monkeypatch):
     #? ['setattr']
     monkeypatch.setatt
 
-# python > 2.7
-
 #? ['capsysbinary']
 def test_p(capsysbin