Revert unneeded customization

patacrep/songs/chordpro/ast.py

@@ -246,7 +246,7 @@ class Song(AST):
             self.meta[data.keyword] = []
         self.meta[data.keyword].append(data)
 
-    def get_data_argument(self, keyword, default=None):
+    def get_data_argument(self, keyword, default):
         """Return `self.meta[keyword].argument`.
 
         Return `default` if `self.meta[keyword]` does not exist.

patacrep/templates.py

@@ -8,7 +8,7 @@ import os
 import re
 import json
 
-from patacrep import errors, files, songs
+from patacrep import errors, files
 from patacrep.latex import lang2babel
 import patacrep.encoding