When a module uses the HttpClient mixin but registers the USERNAME
and PASSWORD datastore options in order to perform a form auth,
it ruins the ability to also perform a basic auth (sometimes it's
possible to see both). To avoid option naming conflicts, basic auth
options are now HTTPUSERNAME and HTTPPASSWORD.
Fix#4885
See the complaint on #4039. This doesn't fix that particular
issue (it's somewhat unrelated), but does solve around
a file parsing problem reported by @void-in
Alan Foster