rework all the logic for the zip file organization scheme

test_runner/regress/test_download_extensions.py

@@ -1,17 +1,14 @@
-import json
 from contextlib import closing
 
 import pytest
 from fixtures.log_helper import log
 from fixtures.neon_fixtures import (
     NeonEnvBuilder,
-    PgBin,
     RemoteStorageKind,
     available_s3_storages,
 )
 from fixtures.pg_version import PgVersion
 
-
 # Generate mock extension files and upload them to the mock bucket.
 #
 # NOTE: You must have appropriate AWS credentials to run REAL_S3 test.