More effectively disable the helper class when pure virtual methods are found that cannot be generated.

pybindgen/cppclass.py

@@ -680,6 +680,11 @@ public:
         if self.have_pure_virtual_methods and self.helper_class is None:
             self.cannot_be_constructed = True
 
+    def set_helper_class_disabled(self, flag=True):
+        self.helper_class_disabled = flag
+        if flag:
+            self.helper_class = None
+
     def set_cannot_be_constructed(self, flag=True):
         self.cannot_be_constructed = flag
 

pybindgen/gccxmlparser.py

@@ -600,6 +600,7 @@ class ModuleParser(object):
                                            Warning, member.location.file_name, member.location.line)
                     if pure_virtual:
                         class_wrapper.set_cannot_be_constructed(True)
+                        class_wrapper.set_helper_class_disabled(True)
                     continue
                 arguments = []
                 ok = True
@@ -615,6 +616,7 @@ class ModuleParser(object):
                 if not ok:
                     if pure_virtual:
                         class_wrapper.set_cannot_be_constructed(True)
+                        class_wrapper.set_helper_class_disabled(True)
                     continue
 
                 if pure_virtual and not class_wrapper.allow_subclassing: