views: check if image fits in cache before /cache/fetch

Check if the image fits in cache before a /cache/fetch request.
Report the clients unable to store the image.

ogcp/views.py

@@ -1411,6 +1411,17 @@ def action_image_fetch():
             flash(_(f'Image to fetch was not found'), category='error')
             return redirect(url_for('commands'))
 
+        r = server.get('/cache/list', payload={'clients': ips})
+        if not r:
+            return ogserver_down('commands')
+        if r.status_code != requests.codes.ok:
+            return ogserver_error('commands')
+
+        clients_info = r.json()['clients']
+
+        if not image_fits_in_cache(server, clients_info, image):
+            return redirect(url_for('commands'))
+
         payload = {'clients': ips,
                    'repository_id': image['repo_id'],
                    'type': form.method.data,