Prepare 5.0.0 (#1123)

* Bump version to 5.0.0-a1.

* Drop support for ansible-core 2.15 and 2.16.

* Remove Python 2 and early Python 3 compatibility.

tests/unit/plugins/test_support/docker_image_archive_stubbing.py

@@ -37,8 +37,7 @@ def write_imitation_archive(file_name, image_id, repo_tags):
 
 
 def write_imitation_archive_with_manifest(file_name, manifest):
-    tf = tarfile.open(file_name, 'w')
-    try:
+    with tarfile.open(file_name, 'w') as tf:
         with TemporaryFile() as f:
             f.write(json.dumps(manifest).encode('utf-8'))
 
@@ -48,10 +47,6 @@ def write_imitation_archive_with_manifest(file_name, manifest):
             f.seek(0)
             tf.addfile(ti, f)
 
-    finally:
-        # In Python 2.6, this does not have __exit__
-        tf.close()
-
 
 def write_irrelevant_tar(file_name):
     '''