Refactor and implement download code natively

- Use modified port of Django 2.2 FileResponse.
- Remove Django DownloadView library.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/common/tests/base.py

@@ -2,8 +2,6 @@ from __future__ import absolute_import, unicode_literals
 
 from django.test import TestCase
 
-from django_downloadview import assert_download_response
-
 from mayan.apps.acls.tests.mixins import ACLTestCaseMixin
 from mayan.apps.converter.tests.mixins import LayerTestCaseMixin
 from mayan.apps.permissions.tests.mixins import PermissionTestCaseMixin
@@ -14,7 +12,7 @@ from mayan.apps.user_management.tests.mixins import UserTestMixin
 
 from .mixins import (
     ClientMethodsTestCaseMixin, ConnectionsCheckTestCaseMixin,
-    ContentTypeCheckTestCaseMixin, ModelTestCaseMixin,
+    ContentTypeCheckTestCaseMixin, DownloadTestCaseMixin, ModelTestCaseMixin,
     OpenFileCheckTestCaseMixin, RandomPrimaryKeyModelMonkeyPatchMixin,
     SilenceLoggerTestCaseMixin, TempfileCheckTestCasekMixin,
     TestViewTestCaseMixin
@@ -22,7 +20,8 @@ from .mixins import (
 
 
 class BaseTestCase(
-    LayerTestCaseMixin, SilenceLoggerTestCaseMixin, ConnectionsCheckTestCaseMixin,
+    LayerTestCaseMixin, SilenceLoggerTestCaseMixin,
+    ConnectionsCheckTestCaseMixin, DownloadTestCaseMixin,
     RandomPrimaryKeyModelMonkeyPatchMixin, ACLTestCaseMixin,
     ModelTestCaseMixin, OpenFileCheckTestCaseMixin, PermissionTestCaseMixin,
     SmartSettingsTestCaseMixin, TempfileCheckTestCasekMixin, UserTestMixin,
@@ -31,7 +30,6 @@ class BaseTestCase(
     """
     This is the most basic test case class any test in the project should use.
     """
-    assert_download_response = assert_download_response
 
 
 class GenericViewTestCase(

mayan/apps/common/tests/mixins.py

@@ -18,12 +18,16 @@ from django.http import HttpResponse
 from django.template import Context, Template
 from django.test.utils import ContextList
 from django.urls import clear_url_caches, reverse
-from django.utils.encoding import force_bytes
+from django.utils.encoding import (
+    DjangoUnicodeDecodeError, force_bytes, force_text
+)
 from django.utils.six import PY3
 
 from mayan.apps.acls.classes import ModelPermission
 from mayan.apps.storage.settings import setting_temporary_directory
 
+from ..compat import FileResponse
+
 from .literals import (
     TEST_SERVER_HOST, TEST_SERVER_SCHEME, TEST_VIEW_NAME, TEST_VIEW_URL
 )
@@ -141,6 +145,37 @@ class ContentTypeCheckTestCaseMixin(object):
         self.client = CustomClient()
 
 
+class DownloadTestCaseMixin(object):
+    def assert_download_response(
+        self, response, content=None, filename=None, is_attachment=None,
+        mime_type=None
+    ):
+        self.assertTrue(isinstance(response, FileResponse))
+
+        if filename:
+            self.assertEqual(
+                response[
+                    'Content-Disposition'
+                ].split('filename="')[1].split('"')[0], filename
+            )
+
+        if content:
+            response_content = b''.join(list(response))
+
+            try:
+                response_content = force_text(response_content)
+            except DjangoUnicodeDecodeError:
+                """Leave as bytes"""
+
+            self.assertEqual(response_content, content)
+
+        if is_attachment is not None:
+            self.assertEqual(response['Content-Disposition'], 'attachment')
+
+        if mime_type:
+            self.assertTrue(response['Content-Type'].startswith(mime_type))
+
+
 class EnvironmentTestCaseMixin(object):
     def setUp(self):
         super(EnvironmentTestCaseMixin, self).setUp()