Add test for correct handling of albumartistsort as TSO2

This tests that albumartistsort is handled by the TSO2 frameid.

tests/test_easyid3.py

@@ -3,7 +3,7 @@
 import pickle
 
 from mutagen import MutagenError
-from mutagen.id3 import ID3FileType, ID3, RVA2, CHAP, TDRC, CTOC
+from mutagen.id3 import ID3FileType, ID3, RVA2, CHAP, TDRC, CTOC, TSO2
 from mutagen.easyid3 import EasyID3, error as ID3Error
 
 from tests import TestCase, DATA_DIR, get_temp_copy
@@ -428,3 +428,9 @@ def test_text_tags(self):
             self.id3.save(self.filename)
             id3 = EasyID3(self.filename)
             self.failUnlessEqual(id3[tag], [u"foo"])
+
+    def test_albumartistsort(self):
+        self.realid3.add(TSO2(text=u"someartist"))
+        self.id3.save(self.filename)
+        id3 = EasyID3(self.filename)
+        self.failUnlessEqual(id3["albumartistsort"], [u"someartist"])