Fix IMAP4 store flags argument, GitLab issue #606

Python's documentation is incorrect, argument name is flag_list.
Closes GitLab issue #606. Thanks to Samuel Aebi (@samuelaebi)
for the report and debug information.

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

mayan/apps/sources/tests/test_models.py

@@ -20,8 +20,9 @@ from mayan.apps.metadata.models import MetadataType
 from mayan.apps.storage.utils import mkdtemp
 
 from ..literals import SOURCE_UNCOMPRESS_CHOICE_Y
-from ..models import POP3Email, WatchFolderSource, WebFormSource
-from ..models.email_sources import EmailBaseModel
+from ..models.email_sources import EmailBaseModel, IMAPEmail, POP3Email
+from ..models.watch_folder_sources import WatchFolderSource
+from ..models.webform_sources import WebFormSource
 
 from .literals import (
     TEST_EMAIL_ATTACHMENT_AND_INLINE, TEST_EMAIL_BASE64_FILENAME,
@@ -60,7 +61,7 @@ class CompressedUploadsTestCase(GenericDocumentTestCase):
         )
 
 
-class EmailFilenameDecodingTestCase(GenericDocumentTestCase):
+class EmailBaseTestCase(GenericDocumentTestCase):
     auto_upload_document = False
 
     def _create_email_source(self):
@@ -190,6 +191,55 @@ class EmailFilenameDecodingTestCase(GenericDocumentTestCase):
         self.assertEqual(2, Document.objects.count())
 
 
+class IMAPSourceTestCase(GenericDocumentTestCase):
+    auto_upload_document = False
+
+    class MockIMAPServer(object):
+        def login(self, user, password):
+            return ('OK', ['{} authenticated (Success)'.format(user)])
+
+        def select(self, mailbox='INBOX', readonly=False):
+            return ('OK', ['1'])
+
+        def search(self, charset, *criteria):
+            return ('OK', ['1'])
+
+        def fetch(self, message_set, message_parts):
+            return (
+                'OK', [
+                    (
+                        '1 (RFC822 {4800}',
+                        TEST_EMAIL_BASE64_FILENAME
+                    ), ' FLAGS (\\Seen))'
+                ]
+            )
+
+        def store(self, message_set, command, flags):
+            return ('OK', ['1 (FLAGS (\\Seen \\Deleted))'])
+
+        def expunge(self):
+            return ('OK', ['1'])
+
+        def close(self):
+            return ('OK', ['Returned to authenticated state. (Success)'])
+
+        def logout(self):
+            return ('BYE', ['LOGOUT Requested'])
+
+    @mock.patch('imaplib.IMAP4_SSL', autospec=True)
+    def test_download_document(self, mock_imaplib):
+        mock_imaplib.return_value = IMAPSourceTestCase.MockIMAPServer()
+        self.source = IMAPEmail.objects.create(
+            document_type=self.test_document_type, label='', host='',
+            password='', username=''
+        )
+
+        self.source.check_source()
+        self.assertEqual(
+            Document.objects.first().label, 'Ampelm\xe4nnchen.txt'
+        )
+
+
 class POP3SourceTestCase(GenericDocumentTestCase):
     auto_upload_document = False