Doc: Adding note to use the '--use-slo' option for swift large object…

…s. (#2385) [skip travis] [skip appveyor]

gdal/doc/source/user/virtual_file_systems.rst

@@ -393,7 +393,9 @@ Three authentication methods are possible, and are attempted in the following or
    - `OS_PROJECT_DOMAIN_NAME`
    - `OS_REGION_NAME`
 
-This file system handler also allows sequential writing of files (no seeks or read operations are then allowed)
+This file system handler also allows sequential writing of files (no seeks or read operations are then allowed).
+
+In some versions of OpenStack Swift, the access to large (segmented) files fails unless they are explicitly marked as static large objects, instead of being dynamic large objects which is the default. Using the python-swiftclient this can be achieved when uploading the file by passing the ``--use-slo`` flag (see https://docs.openstack.org/python-swiftclient/latest/cli/index.html#swift-upload for all options). For more information about large objects see https://docs.openstack.org/swift/latest/api/large_objects.html.
 
 .. versionadded:: 2.3