PEP8 cleanups.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/cabinets/widgets.py

@@ -1,12 +1,11 @@
 from __future__ import unicode_literals
 
 from django.apps import apps
-from django.template.loader import render_to_string
 from django.utils.html import format_html_join
-from django.utils.safestring import mark_safe
 
 from .permissions import permission_cabinet_view
 
+
 def jstree_data(node, selected_node):
     result = []
     result.append('{')
@@ -51,4 +50,4 @@ def widget_document_cabinets(document, user):
         (
             (cabinet.get_full_path(),) for cabinet in cabinets
         )
-    )
+    )