Fix compatibility kludge to work with older packaging

Fixes pypa#1216.

changelog/1217.bugfix.rst

@@ -0,0 +1,2 @@
+Fix compatibility kludge for invalid License-File metadata entries emitted by
+build backends to work also with ``packaging`` version 24.0.

twine/package.py

@@ -214,14 +214,7 @@ def from_filename(cls, filename: str, comment: Optional[str]) -> "PackageFile":
 
         # Parse and validate metadata.
         meta, unparsed = metadata.parse_email(data)
-        if unparsed:
-            raise exceptions.InvalidDistribution(
-                "Invalid distribution metadata: {}".format(
-                    "; ".join(
-                        f"unrecognized or malformed field {key!r}" 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
@@ -232,6 +225,21 @@ def from_filename(cls, filename: str, comment: Optional[str]) -> "PackageFile":
         # than 2.4.
         if version.Version(meta.get("metadata_version", "0")) < version.Version("2.4"):
             meta.pop("license_files", None)
+            # Support for metadata version 2.4 requires packaging version 24.1
+            # or lalet. When parsing invalid metadata with an older packagign,
+            # the invalid License-File fileds are not understood and added to
+            # the unparsed dictionary.
+            unparsed.pop("license-file", None)
+
+        if unparsed:
+            raise exceptions.InvalidDistribution(
+                "Invalid distribution metadata: {}".format(
+                    "; ".join(
+                        f"unrecognized or malformed field {key!r}" for key in unparsed
+                    )
+                )
+            )
+
         try:
             metadata.Metadata.from_raw(meta)
         except metadata.ExceptionGroup as group: