Fix (obsolete) forward declared C++ subclass declarations.

Cython/Compiler/Nodes.py

@@ -1186,7 +1186,7 @@ class CppClassNode(CStructOrUnionDefNode):
         scope = None
         if self.attributes is not None:
             scope = CppClassScope(self.name, env, templates = self.templates)
-        base_class_types = [b.analyse(scope) for b in self.base_classes]
+        base_class_types = [b.analyse(scope or env) for b in self.base_classes]
         if self.templates is None:
             template_types = None
         else:

Cython/Compiler/Symtab.py

@@ -2028,6 +2028,8 @@ class CppClassScope(Scope):
                 self.default_constructor = True
                 return
             for base_class in entry.type.base_classes:
+                if base_class is PyrexTypes.error_type:
+                    continue
                 temp_entry = base_class.scope.lookup_here("<init>")
                 found = False
                 if temp_entry is None: