Fix flake8 problems

Author: abravalheri

setuptools/tests/config/downloads/__init__.py

@@ -1,4 +1,3 @@
-import io
 import re
 from pathlib import Path
 from urllib.request import urlopen

setuptools/tests/config/test_apply_pyprojecttoml.py

@@ -5,7 +5,6 @@
 import re
 import tarfile
 from pathlib import Path
-from urllib.request import urlopen
 from unittest.mock import Mock
 from zipfile import ZipFile