Standardize error type for all _distutils.modified methods

mypy.ini

@@ -30,7 +30,8 @@ disable_error_code = attr-defined
 [mypy-pkg_resources.tests.*]
 disable_error_code = import-not-found
 
-# - distutils._modified has different errors on Python 3.8 [import-untyped], on Python 3.9+ [import-not-found]
+# - distutils._modified has different errors on Python 3.8 on Windows only [import-untyped],
+#   where it's an [import-not-found] on all other platforms and versions
 # - All jaraco modules are still untyped
 # - _validate_project sometimes complains about trove_classifiers (#4296)
 # - wheel appears to be untyped

newsfragments/4567.bugfix.rst

@@ -0,0 +1 @@
+Ensured all methods in `setuptools.modified` raise a consistant `distutils.error.DistutilsError` type -- by :user:`Avasam`

setuptools/command/build_clib.py

@@ -1,13 +1,9 @@
+from ..modified import newer_pairwise_group
+
 import distutils.command.build_clib as orig
 from distutils import log
 from distutils.errors import DistutilsSetupError
 
-try:
-    from distutils._modified import newer_pairwise_group
-except ImportError:
-    # fallback for SETUPTOOLS_USE_DISTUTILS=stdlib
-    from .._distutils._modified import newer_pairwise_group
-
 
 class build_clib(orig.build_clib):
     """

setuptools/modified.py

@@ -1,8 +1,18 @@
-from ._distutils._modified import (
-    newer,
-    newer_group,
-    newer_pairwise,
-    newer_pairwise_group,
-)
+try:
+    # Ensure a DistutilsError raised by these methods is the same as distutils.error.DistutilsError
+    from distutils._modified import (
+        newer,
+        newer_group,
+        newer_pairwise,
+        newer_pairwise_group,
+    )
+except ImportError:
+    # fallback for SETUPTOOLS_USE_DISTUTILS=stdlib, because _modified never existed in stdlib
+    from ._distutils._modified import (
+        newer,
+        newer_group,
+        newer_pairwise,
+        newer_pairwise_group,
+    )
 
 __all__ = ['newer', 'newer_pairwise', 'newer_group', 'newer_pairwise_group']