Accommodate for invalid metadata produced by setuptools

See pypa/setuptools#4759.

twine/package.py

@@ -21,6 +21,7 @@
 from typing import Any, Dict, List, NamedTuple, Optional, Sequence, Tuple, Union
 
 from packaging import metadata
+from packaging import version
 from rich import print
 
 from twine import bdist
@@ -143,6 +144,16 @@ def from_filename(cls, filename: str, comment: Optional[str]) -> "PackageFile":
                     for key in unparsed
                 )
             )
+        # setuptools emits License-File metadata fields while declaring
+        # Metadata-Version 2.1. This is invalid because the metadata
+        # specification does not allow to add arbitrary fields, and because
+        # the semantic implemented by setuptools is different than the one
+        # described in PEP 639. However, rejecting these packages would be
+        # too disruptive. Drop License-File metadata entries from the data
+        # sent to the package index if the declared metadata version is less
+        # than 2.4.
+        if version.Version(meta.get("metadata_version", "0")) < version.Version("2.4"):
+            meta.pop("license_files", None)
         try:
             metadata.Metadata.from_raw(meta)
         except metadata.ExceptionGroup as group: