Fix sources app setting migrations

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

HISTORY.rst

@@ -2,6 +2,7 @@
 ==================
 - Improve setting migration method matching. Avoid executing
   a migrations for settings with similar but shorter names.
+- Fix sources app setting migrations.
 
 3.3.1 (2019-12-04)
 ==================

mayan/apps/sources/setting_migrations.py

@@ -9,7 +9,7 @@ class SourcesSettingMigration(NamespaceMigration):
     From version 0001 to 0002 backend arguments are no longer quoted
     but YAML valid too. Changed in version 3.3.
     """
-    def sources_staging_file_cache_storage_backend_arguments(self, value):
+    def sources_staging_file_cache_storage_backend_arguments_0001(self, value):
         return yaml_load(
             stream=value or '{}',
         )

mayan/apps/sources/tests/test_setting_migrations.py

@@ -0,0 +1,35 @@
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.utils.encoding import force_bytes
+
+from mayan.apps.common.tests.base import BaseTestCase
+from mayan.apps.common.tests.mixins import EnvironmentTestCaseMixin
+from mayan.apps.smart_settings.classes import Setting
+from mayan.apps.storage.utils import NamedTemporaryFile
+
+from ..settings import setting_staging_file_image_cache_storage_arguments
+
+
+class SourceSettingMigrationTestCase(EnvironmentTestCaseMixin, BaseTestCase):
+    def test_setting_staging_file_image_cache_storage_arguments_0001_migration(self):
+
+        test_value = {'location': 'test value'}
+
+        with NamedTemporaryFile() as file_object:
+            settings.CONFIGURATION_FILEPATH = file_object.name
+            file_object.write(
+                force_bytes(
+                    '{}: {}'.format(
+                        'SOURCES_STAGING_FILE_CACHE_STORAGE_BACKEND_ARGUMENTS',
+                        '"{}"'.format(Setting.serialize_value(value=test_value))
+                    )
+                )
+            )
+            file_object.seek(0)
+            Setting._config_file_cache = None
+
+            self.assertEqual(
+                setting_staging_file_image_cache_storage_arguments.value,
+                test_value
+            )