Fix s3utils errors

Add docstring to the clean_test_environment function

python/lsst/resources/s3utils.py

@@ -11,7 +11,13 @@
 
 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from unittest import TestCase
+
 __all__ = (
+    "clean_test_environment",
     "getS3Client",
     "s3CheckFileExists",
     "bucketExists",
@@ -108,6 +114,27 @@ class _TooManyRequestsException(Exception):
 max_retry_time = 60
 
 
+def clean_test_environment(testcase: TestCase) -> None:
+    """Clear S3_ENDPOINT_URL then reset it at the end of a test.
+
+    Parameters
+    ----------
+    testcase: `TestCase`, `self`
+        Reference to the test being run; used to add a cleanup function.
+    """
+    endpoint = os.environ.get("S3_ENDPOINT_URL")
+
+    if not endpoint:
+        return
+    os.environ["S3_ENDPOINT_URL"] = ""
+
+    def cleanup() -> None:
+        if endpoint is not None:
+            os.environ["S3_ENDPOINT_URL"] = endpoint
+
+    testcase.addCleanup(cleanup)
+
+
 def getS3Client() -> boto3.client:
     """Create a S3 client with AWS (default) or the specified endpoint.
 

tests/test_s3.py

@@ -9,10 +9,10 @@
 # Use of this source code is governed by a 3-clause BSD-style
 # license that can be found in the LICENSE file.
 
-import os
 import unittest
 
 from lsst.resources import ResourcePath
+from lsst.resources.s3utils import clean_test_environment
 from lsst.resources.tests import GenericReadWriteTestCase, GenericTestCase
 
 try:
@@ -44,11 +44,7 @@ def setUp(self):
         # Enable S3 mocking of tests.
         self.mock_s3.start()
 
-        self.endpoint = None
-
-        if "S3_ENDPOINT_URL" in os.environ:
-            self.endpoint = os.environ["S3_ENDPOINT_URL"]
-            os.environ["S3_ENDPOINT_URL"] = ""
+        clean_test_environment(self)
 
         # set up some fake credentials if they do not exist
         # self.usingDummyCredentials = setAwsEnvCredentials()
@@ -74,9 +70,6 @@ def tearDown(self):
         bucket = s3.Bucket(self.netloc)
         bucket.delete()
 
-        if self.endpoint is not None:
-            os.environ["S3_ENDPOINT_URL"] = self.endpoint
-
         # Stop the S3 mock.
         self.mock_s3.stop()
 

tests/test_s3utils.py

@@ -21,6 +21,8 @@
 
 import unittest
 
+from lsst.resources.s3utils import clean_test_environment
+
 try:
     import boto3
     from moto import mock_s3
@@ -55,6 +57,8 @@ def setUp(self):
         # set up some fake credentials if they do not exist
         self.usingDummyCredentials = setAwsEnvCredentials()
 
+        clean_test_environment(self)
+
         self.client = getS3Client()
         try:
             self.client.create_bucket(Bucket=self.bucketName)