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.

app/main/views/send.py

@@ -21,6 +21,7 @@ from notifications_utils.recipients import (
     first_column_headings,
     optional_address_columns,
 )
+from notifications_utils.sanitise_text import SanitiseASCII
 from orderedset import OrderedSet
 from werkzeug.routing import RequestRedirect
 from xlrd.biffh import XLRDError
@@ -576,7 +577,7 @@ def _check_messages(service_id, template_id, upload_id, preview_row, letters_as_
         row_errors=get_errors_for_csv(recipients, template.template_type),
         count_of_recipients=len(recipients),
         count_of_displayed_recipients=len(list(recipients.displayed_rows)),
-        original_file_name=request.args.get('original_file_name'),
+        original_file_name=request.args.get('original_file_name', ''),
         upload_id=upload_id,
         form=CsvUploadForm(),
         remaining_messages=remaining_messages,
@@ -619,6 +620,8 @@ def check_messages(service_id, template_id, upload_id, row_index=2):
     ):
         return render_template('views/check/column-errors.html', **data)
 
+    data['original_file_name'] = SanitiseASCII.encode(data.get('original_file_name', ''))
+
     set_metadata_on_csv_upload(
         service_id,
         upload_id,
@@ -626,7 +629,7 @@ def check_messages(service_id, template_id, upload_id, row_index=2):
         template_id=str(template_id),
         valid=True,
         original_file_name=unicode_truncate(
-            request.args.get('original_file_name', ''),
+            data['original_file_name'],
             1600,
         ),
     )