Remove Python 3.5 & 3.6 compat code in tests

[bskinn]

sphobjinv/conftest.py

Lines 145 to 149 in ae11a0e

	# The str() calls here are for Python 3.5 compat
	shutil.copy(
	str(res_path / f"{res_base}{ext}"),
	str(tmp_path / f"{scr_base}{ext}"),
	)

sphobjinv/tests/test_flake8_ext.py

Lines 53 to 56 in ae11a0e

	@pytest.mark.skipif(
	sys.version_info < (3, 6),
	reason="Some flake8 extensions require Python 3.6 or later",
	)