remove art_filename Library field

This is the first of a handful of refactorings that take advantage of the new
confit system to simplify parameter passing boilerplate.

beets/library.py

@@ -1113,7 +1113,6 @@ class Library(BaseLibrary):
                        directory='~/Music',
                        path_formats=((PF_KEY_DEFAULT,
                                       '$artist/$album/$track $title'),),
-                       art_filename='cover',
                        timeout=5.0,
                        replacements=None,
                        item_fields=ITEM_FIELDS,
@@ -1124,7 +1123,6 @@ class Library(BaseLibrary):
             self.path = bytestring_path(normpath(path))
         self.directory = bytestring_path(normpath(directory))
         self.path_formats = path_formats
-        self.art_filename = art_filename
         self.replacements = replacements
 
         self._memotable = {}  # Used for template substitution performance.
@@ -1703,11 +1701,9 @@ class Album(BaseAlbum):
         image = bytestring_path(image)
         item_dir = item_dir or self.item_dir()
 
-        if not isinstance(self._library.art_filename,Template):
-            self._library.art_filename = Template(self._library.art_filename)
-
+        filename_tmpl = Template(beets.config['art_filename'].get(unicode))
         subpath = util.sanitize_path(format_for_path(
-            self.evaluate_template(self._library.art_filename)
+            self.evaluate_template(filename_tmpl)
         ))
         subpath = bytestring_path(subpath)
 

beets/ui/__init__.py

@@ -729,7 +729,6 @@ def _raw_main(args):
             dbpath,
             config['directory'].as_filename(),
             get_path_formats(),
-            Template(config['art_filename'].get(unicode)),
             config['timeout'].as_number(),
             get_replacements(),
         )

test/test_db.py

@@ -29,6 +29,7 @@ from _common import item
 import beets.library
 from beets import util
 from beets import plugins
+from beets import config
 
 TEMP_LIB = os.path.join(_common.RSRC, 'test_copy.blb')
 
@@ -835,10 +836,10 @@ class BaseAlbumTest(_common.TestCase):
 class ArtDestinationTest(_common.TestCase):
     def setUp(self):
         super(ArtDestinationTest, self).setUp()
+        config['art_filename'] = u'artimage'
         self.lib = beets.library.Library(':memory:')
         self.i = item()
         self.i.path = self.lib.destination(self.i)
-        self.lib.art_filename = 'artimage'
         self.ai = self.lib.add_album((self.i,))
 
     def test_art_filename_respects_setting(self):