Add convert_path back (but with deprecated status)

changelog.d/3206.deprecation.rst

@@ -0,0 +1,3 @@
+Changed ``setuptools.convert_path`` to an internal function that is not exposed
+as part of setuptools API.
+Future releases of ``setuptools`` are likely to remove this function.

setuptools/__init__.py

@@ -3,11 +3,13 @@
 import functools
 import os
 import re
+import warnings
 
 import _distutils_hack.override  # noqa: F401
 
 import distutils.core
 from distutils.errors import DistutilsOptionError
+from distutils.util import convert_path as _convert_path
 
 from ._deprecation_warning import SetuptoolsDeprecationWarning
 
@@ -158,6 +160,19 @@ def findall(dir=os.curdir):
     return list(files)
 
 
+@functools.wraps(_convert_path)
+def convert_path(pathname):
+    from inspect import cleandoc
+
+    msg = """
+    The function `convert_path` is considered internal and not part of the public API.
+    Its direct usage by 3rd-party packages is considered deprecated and the function
+    may be removed in the future.
+    """
+    warnings.warn(cleandoc(msg), SetuptoolsDeprecationWarning)
+    return _convert_path(pathname)
+
+
 class sic(str):
     """Treat this string as-is (https://en.wikipedia.org/wiki/Sic)"""
 

setuptools/tests/test_setuptools.py

@@ -303,3 +303,8 @@ def test_its_own_wheel_does_not_contain_tests(setuptools_wheel):
 
     for member in contents:
         assert '/tests/' not in member
+
+
+def test_convert_path_deprecated():
+    with pytest.warns(setuptools.SetuptoolsDeprecationWarning):
+        setuptools.convert_path('setuptools/tests')