Fix deprecation warnings for Django 1.11 and Django 2.0.

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

mayan/apps/django_gpg/models.py

@@ -4,8 +4,8 @@ from datetime import date
 import logging
 
 from django.core.exceptions import ValidationError
-from django.core.urlresolvers import reverse
 from django.db import models
+from django.urls import reverse
 from django.utils.encoding import python_2_unicode_compatible
 from django.utils.translation import ugettext_lazy as _
 

mayan/apps/django_gpg/tests/test_api.py

@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
 
 from django.contrib.auth import get_user_model
-from django.core.urlresolvers import reverse
 from django.test import override_settings
+from django.urls import reverse
 
 from rest_api.tests import BaseAPITestCase
 from user_management.tests.literals import (

mayan/apps/django_gpg/views.py

@@ -4,7 +4,7 @@ import logging
 
 from django.contrib import messages
 from django.core.files.base import ContentFile
-from django.core.urlresolvers import reverse, reverse_lazy
+from django.urls import reverse, reverse_lazy
 from django.utils.translation import ugettext_lazy as _
 
 from common.generics import (