I would like to test Odoo 9. I have it installed on CentOS 7. I had installed lessc, but while loading i'm getting this error:

WARNING odoo_9_alpha openerp.addons.base.ir.ir_qweb: /usr/local/share/gems/gems/less-2.6.0/bin/lessc:83:in `<top (required)>': invalid option: --clean-css (OptionParser::InvalidOption)

from /usr/local/bin/lessc:23:in `load'

from /usr/local/bin/lessc:23:in `<main>'

This error occured while compiling the bundle 'web.assets_backend' containing:

- /website/static/src/less/import_bootstrap.less

- /web/static/src/less/enterprise_compatibility.less

- /web/static/src/less/utils.less

- /web/static/src/less/modal.less

- /web_calendar/static/src/less/web_calendar.less

- /web_kanban/static/src/less/kanban_dashboard.less

- /web_kanban/static/src/less/kanban_view.less

Layout of page is broken. Does anybody know what it could mean?