Sanitise csv filenames before saving to S3

Commit 58cc1604a7 sanitises any non-ascii
characters in the headers. CSV filenames get used as a header value, so
this fixed a bug that occurred when non-ascii characters were used.

The CSV filename also gets used as part of the metadata when uploading
the file to S3. Since the S3 metadata can only contain ASII characters,
we also need to sanitise the filename before uploading it to S3.

tests/app/main/views/test_send.py

@@ -765,7 +765,48 @@ def test_file_name_truncated_to_fit_in_s3_metadata(
     assert sys.getsizeof(''.join((
         '{}{}'.format(key, value) for key, value in
         mock_s3_set_metadata.call_args_list[0][1].items()
-    )).encode('utf-8')) == 1724
+    )).encode('utf-8')) == 1726
+
+
+def test_check_messages_replaces_invalid_characters_in_file_name(
+    client_request,
+    mocker,
+    mock_get_live_service,
+    mock_get_service_template_with_placeholders,
+    mock_get_users_by_service,
+    mock_get_service_statistics,
+    mock_get_job_doesnt_exist,
+    mock_s3_set_metadata,
+    fake_uuid,
+):
+    with client_request.session_transaction() as session:
+        session['file_uploads'] = {
+            fake_uuid: {'template_id': fake_uuid}
+        }
+
+    mocker.patch('app.main.views.send.s3download', return_value="""
+        phone number,name,thing,thing,thing
+        07700900001, A,   foo,  foo,  foo
+    """)
+
+    file_name = 'ü😁’€'
+
+    client_request.get(
+        'main.check_messages',
+        service_id=SERVICE_ONE_ID,
+        template_id=fake_uuid,
+        upload_id=fake_uuid,
+        original_file_name=file_name,
+    )
+
+    mock_s3_set_metadata.assert_called_once_with(
+        SERVICE_ONE_ID,
+        fake_uuid,
+        notification_count=1,
+        original_file_name="u?'?",
+        template_id=fake_uuid,
+        valid=True
+    )
 
 
 def test_show_all_columns_if_there_are_duplicate_recipient_columns(