exts: support < 3.9 extensions

Author: gpotter2

scapy/config.py

@@ -652,7 +652,10 @@ def load(self, extension: str):
             return
 
         # Check the classifiers
-        if distr.metadata.get('License-Expression', None) not in self.GPLV2_LICENCES:
+        if (
+            distr.metadata.get('License-Expression', None) not in self.GPLV2_LICENCES
+            and distr.metadata.get('License', None) not in self.GPLV2_LICENCES
+        ):
             log_loading.warning(
                 "'%s' has no GPLv2 classifier therefore cannot be loaded." % extension
             )