Add support for Core metadata specification 2.3 and 2.4

Signed-off-by: Lumir Balhar <lbalhar@redhat.com>

Author: frenzymadness

pkginfo2/distribution.py

@@ -67,13 +67,20 @@ def _collapse_leading_ws(header, txt):
     ('Dynamic', 'dynamic', True),
 )
 
+HEADER_ATTRS_2_4 = HEADER_ATTRS_2_2 + ( # PEP 639
+    ('License-Expression', 'license_expression', False),
+    ('License-Files', 'license_files', True),
+)
+
 HEADER_ATTRS = {
     '1.0': HEADER_ATTRS_1_0,
     '1.1': HEADER_ATTRS_1_1,
     '1.2': HEADER_ATTRS_1_2,
     '2.0': HEADER_ATTRS_2_0,
     '2.1': HEADER_ATTRS_2_1,
     '2.2': HEADER_ATTRS_2_2,
+    '2.3': HEADER_ATTRS_2_2,
+    '2.4': HEADER_ATTRS_2_4,
 }
 
 class Distribution(object):
@@ -110,6 +117,9 @@ class Distribution(object):
     description_content_type = None
     # version 2.2
     dynamic = ()
+    # version 2.4
+    license_expression = None
+    license_files = ()
 
     def extractMetadata(self):
         data = self.read()