List data files are listed in the Distribution attribute 'data_files',
rather than 'data'.
diff --git a/Lib/distutils/dist.py b/Lib/distutils/dist.py
index 998cff7..24c8d2b 100644
--- a/Lib/distutils/dist.py
+++ b/Lib/distutils/dist.py
@@ -155,7 +155,7 @@
         self.include_dirs = None
         self.extra_path = None
         self.scripts = None
-        self.data = None
+        self.data_files = None
 
         # And now initialize bookkeeping stuff that can't be supplied by
         # the caller at all.  'command_obj' maps command names to