fix duplicate broadcast message issue

capsulflask/__init__.py

@@ -15,6 +15,7 @@ from flask import render_template
 from flask import url_for
 from flask import current_app
 from flask import flash
+from flask import session
 from apscheduler.schedulers.background import BackgroundScheduler
 
 
@@ -210,6 +211,10 @@ def security_headers(response):
   response.headers['X-Content-Type-Options'] = 'nosniff'
 
   if current_app.config['BROADCAST_BANNER_MESSAGE'] is not None and current_app.config['BROADCAST_BANNER_MESSAGE'] != "":
+    for t in session.get("_flashes", []):
+      if t is not None and t[1] == current_app.config['BROADCAST_BANNER_MESSAGE']:
+        return response
+
     flash(current_app.config['BROADCAST_BANNER_MESSAGE'])
 
   return response