Amend changelog for 48.0 to include more detail about usage expectations. Ref #2230.

CHANGES.rst

@@ -16,7 +16,8 @@ v49.0.0
 v48.0.0
 -------
 
-* #2143: Setuptools adopts distutils from the Python 3.9 standard library and no longer depends on distutils in the standard library. When importing ``setuptools`` or ``setuptools.distutils_patch``, Setuptools will expose its bundled version as a top-level ``distutils`` package (and unload any previously-imported top-level distutils package), retaining the expectation that ``distutils``' objects are actually Setuptools objects. Although this change is not expected to break any use cases, it will likely affect tool chains that are monkey-patching distutils or relying on Setuptools' own monkey-patching of distutils.
+* #2143: Setuptools adopts distutils from the Python 3.9 standard library and no longer depends on distutils in the standard library. When importing ``setuptools`` or ``setuptools.distutils_patch``, Setuptools will expose its bundled version as a top-level ``distutils`` package (and unload any previously-imported top-level distutils package), retaining the expectation that ``distutils``' objects are actually Setuptools objects.
+  To avoid getting any legacy behavior from the standard library, projects are advised to always "import setuptools" prior to importing anything from distutils. This behavior happens by default when using ``pip install`` or ``pep517.build``. Workflows that rely on ``setup.py (anything)`` will need to first ensure setuptools is imported. One way to achieve this behavior without modifying code is to invoke Python thus: ``python -c "import setuptools; exec(open('setup.py').read())" (anything)``.
 
 
 v47.3.2