Remove backports for old Python versions

Author: sbraz

setup.cfg

@@ -27,9 +27,6 @@ testing =
 	# upstream
 
 	# local
-	pathlib2
-	contextlib2
-	unittest2
 
 docs =
 	# upstream

test_zipp.py

@@ -6,25 +6,11 @@
 import zipfile
 import posixpath
 import contextlib
+import pathlib
+import unittest
 import tempfile
 import shutil
 
-try:
-    import pathlib
-except ImportError:
-    import pathlib2 as pathlib
-
-if not hasattr(contextlib, 'ExitStack'):
-    import contextlib2
-    contextlib.ExitStack = contextlib2.ExitStack
-
-try:
-    import unittest
-
-    unittest.TestCase.subTest
-except AttributeError:
-    import unittest2 as unittest
-
 import zipp
 
 __metaclass__ = type