Add comments with instructions for developers

Author: abravalheri

setuptools/tests/config/downloads/__init__.py

@@ -9,6 +9,11 @@
 DOWNLOAD_DIR = Path(__file__).parent
 
 
+# ----------------------------------------------------------------------
+# Please update ./preload.py accordingly when modifying this file
+# ----------------------------------------------------------------------
+
+
 def output_file(url: str, download_dir: Path = DOWNLOAD_DIR):
     file_name = url.strip()
     for part in NAME_REMOVE:

setuptools/tests/config/test_apply_pyprojecttoml.py

@@ -1,5 +1,7 @@
 """Make sure that applying the configuration from pyproject.toml is equivalent to
 applying a similar configuration from setup.cfg
+
+To run these tests offline, please have a look on ``./downloads/preload.py``
 """
 import io
 import re