Fix: switch from jinja2.contextfunction to jinja2.pass_context (#278)

patacrep/content/__init__.py

@@ -202,7 +202,7 @@ class EmptyContentList(ContentList):
         for error in errors:
             self.append_error(error)
 
-@jinja2.contextfunction
+@jinja2.pass_context
 def render(context, content):
     """Render the content of the songbook as a LaTeX code.
 

patacrep/songs/chordpro/__init__.py

@@ -6,7 +6,7 @@ import os
 import urllib
 
 from jinja2 import Environment, FileSystemLoader, ChoiceLoader
-from jinja2 import contextfunction
+from jinja2 import pass_context
 import jinja2
 
 from patacrep import encoding, files, pkg_datapath
@@ -88,7 +88,7 @@ class ChordproSong(Song):
             raise NotImplementedError("Cannot convert to format '{}'.".format(self.output_language))
 
     @staticmethod
-    @contextfunction
+    @pass_context
     def _render_ast(context, content):
         """Render ``content``."""
         # context is readonly: create a copy before overriding the 'content' key