[QOL-6619] add error handling for race condition during datastore fil…

…e uploads, ckan#3980

ckan/lib/helpers.py

@@ -28,6 +28,7 @@
 from bleach import clean as bleach_clean, ALLOWED_TAGS, ALLOWED_ATTRIBUTES
 from pylons import url as _pylons_default_url
 from ckan.common import config, is_flask_request
+import ckan.plugins.toolkit as toolkit
 from flask import redirect as _flask_redirect
 from flask import _request_ctx_stack, current_app
 from routes import redirect_to as _routes_redirect_to