Handle duplicate emails on confirmation and make the confirmation error page nicer

data/model.py

@@ -358,6 +358,9 @@ def confirm_user_email(code):
 
   new_email = code.new_email
   if new_email:
+    if find_user_by_email(new_email):
+      raise DataModelException('E-mail address already used.')    
+      
     user.email = new_email
   
   user.save()

endpoints/web.py

@@ -259,7 +259,7 @@ def confirm_email():
   try:
     result = model.confirm_user_email(code)
   except model.DataModelException as ex:
-    return redirect(url_for('signin'))
+      return render_page_template('confirmerror.html', error_message=ex.message)
     
   common_login(result['user'])
 

templates/confirmerror.html

@@ -0,0 +1,20 @@
+{% extends "base.html" %}
+
+{% block title %}
+  <title>Confirmation error · Quay.io</title>
+{% endblock %}
+
+{% block body_content %}
+  <div class="container">
+    <div class="row">
+      <div class="col-md-12">
+        <h2>There was an error confirming your e-mail address.</h2>
+
+        {% if error_message %}
+          <div class="alert alert-danger">{{ error_message }}</div>
+        {% endif %}
+      </div>
+    </div>
+
+  </div>
+{% endblock %}