Add dependency in task_build_pages

nbcourse/nbcourse.py

@@ -313,7 +313,7 @@ class NbCourse:
 
     def task_build_pages(self):
         """Build html pages"""
-        deps = self.md_page_paths + self.theme_files
+        deps = self.executed_notebooks + self.md_page_paths + self.theme_files
         if self.config_file:
             deps.append(self.config_file)
         return {