Change build_dependent_class to only include bases defined in the actual registry

Prior to this commit, the facet registries could not be built correctly as the
dependent classes mro will not be properly ordered.

1 files changed, 6 insertions, 4 deletions

diff --git a/pint/util.py b/pint/util.py
index 2b95765..25b405b 100644
--- a/pint/util.py
+++ b/pint/util.py
@@ -1106,11 +1106,13 @@ def build_dependent_class(registry_class, class_name: str, attribute_name: str)
 
     """
     bases = (
-        getattr(base, attribute_name, None) for base in inspect.getmro(registry_class)
+        getattr(base, attribute_name)
+        for base in inspect.getmro(registry_class)
+        if attribute_name in base.__dict__
     )
-    bases = dict.fromkeys((base for base in bases if base), None)
-
-    return type(class_name, tuple(bases.keys()), dict())
+    bases = dict.fromkeys(bases, None)
+    newcls = type(class_name, tuple(bases.keys()), dict())
+    return newcls
 
 
 def create_class_with_registry(registry, base_class) -> Type: