Fix set_extension running on non-LabThings views

Author: Joel Collins

src/labthings/extensions.py

@@ -9,6 +9,7 @@
 from flask import url_for
 
 from .utilities import camel_to_snake, get_docstring, snake_to_spine
+from .views import View as BaseView
 from .views.builder import static_from
 
 
@@ -110,7 +111,8 @@ def add_view(self, view_class, *urls, endpoint=None, **kwargs):
             self._rules[url] = self._views[endpoint]
 
         # Store this extension name as the View owner
-        view_class.set_extension(self.name)
+        if issubclass(view_class, BaseView):
+            view_class.set_extension(self.name)
 
     def on_register(self, function, args=None, kwargs=None):
         """