Missing import

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/views/source.py

@@ -24,6 +24,7 @@ from django.contrib.auth.decorators import permission_required
 from django.shortcuts import render, redirect, get_object_or_404
 from django.utils.translation import ugettext as _
 from django.views.decorators.http import require_POST
+from django.contrib import messages
 
 from weblate.trans.views.helper import get_subproject
 from weblate.trans.models import Translation, Source