Move iteration of sub-content errors into the ContentList.iter_errors() iterator

patacrep/build.py

@@ -131,10 +131,6 @@ class Songbook:
         yield from self._errors
         contentlist = self._config.get('content', content.ContentList())
         yield from contentlist.iter_errors()
-        for item in contentlist:
-            if not hasattr(item, "iter_errors"):
-                continue
-            yield from item.iter_errors()
 
     def requires_lilypond(self):
         """Tell if lilypond is part of the bookoptions"""

patacrep/content/__init__.py

@@ -185,6 +185,10 @@ class ContentList:
     def iter_errors(self):
         """Iterate over errors."""
         yield from self._errors
+        for item in self:
+            if not hasattr(item, "iter_errors"):
+                continue
+            yield from item.iter_errors()
 
 class EmptyContentList(ContentList):
     """Empty content list: contain only errors."""