PR for ISSUE #104: Flash a message if the user's username does not exists.

app.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-from flask import Flask, render_template, request, session
+from flask import Flask, render_template, request, session, flash
 import logging
 from mysql import connector
 
@@ -112,6 +112,7 @@ def check_username(username):
     result = maulers.fetchall()
     if not result:
         # the user doesnt exist
+        flash("WHOOPS! username could not be found.")
         return False
     else:
         # the user exists

templates/sign_up.html

@@ -39,6 +39,13 @@
             .clear{
                 clear:both;
             }
+            .flash{
+                background-color: azure;
+            }
+            .warning{
+                color: red;    
+            }
+
         </style>
         <title> Sign-in </title>
     </head>
@@ -47,6 +54,15 @@
       {% block content %}
        <div class="main"> 
         <div class="sign_in">
+            <div class="flash warning">
+                {% with messages = get_flashed_messages() %}
+                    {% if messages %}
+                        {% for message in messages %}
+                            {{message}}
+                        {% endfor %}
+                    {% endif %}
+                {% endwith %}
+            </div>
             <h2 class="in"> have an account? Sign-in here</h2>
             <form name="registration" method="post" action=" " >
                 <p>
@@ -95,4 +111,4 @@ <h2 class="up">Don't have an account? Sign-up here</h2>
         </div>
         {% endblock %}
     </body>
-</html>
+</html>