scanner: Have Metadata gracefully handle self.file == NULL

So we don't need to wrap the context manager in a try / except block

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

scanner/metadata.py

@@ -9,11 +9,11 @@ class Metadata:
 
     def __enter__(self):
         self.file = mutagen.File(self.path)
-        return self
+        return self if self.file else None
 
     def __exit__(self, exp_type, exp_value, traceback):
         self.file = None
-        return exp_type == None
+        return (exp_type == None) or (exp_type == AttributeError)
 
     def album(self):
         return self.file.get("album", [ "Unknown Album" ])[0]

scanner/test_metadata.py

@@ -6,6 +6,7 @@ import unittest
 test_tracks  = pathlib.Path("./data/Test Album")
 track_01 = test_tracks / "01 - Test Track.ogg"
 track_02 = test_tracks / "02 - Test {Disc 2}.ogg"
+text_txt = test_tracks / "text.txt"
 
 class TestMetadata(unittest.TestCase):
     def test_metadata_init(self):
@@ -34,3 +35,7 @@ class TestMetadata(unittest.TestCase):
             self.assertEqual(mdf.discsubtitle(), "Electric Boogaloo")
             self.assertEqual(mdf.genres(), [ "Test", "Genre", "List" ])
             self.assertEqual(mdf.year(), 2019)
+
+    def test_metadata_text_txt(self):
+        with scanner.metadata.Metadata(text_txt) as mdf:
+            mdf.artist()