better login and change pwd

templates/change_pwd.html

@@ -1,6 +1,11 @@
 {% extends "base.html" %}
 {% block content %}
 <h3 class="text-center mb-4"><img style="width: 3em; height: 3em" src="/static/login.svg"></h3>
+{% with messages = get_flashed_messages() %}
+  {% for message in messages %}
+    <div class="alert alert-danger" role="alert">{{ message }}</div>
+  {% endfor %}
+{% endwith %}
 <form method="post">
 
   <input class="form-control mb-3" name="password_old" type="password" placeholder="Old Password" required>