script: fix demosite populate
script: fix demosite populate

* Fixes the `inveniomanage demosite populate` command.

Signed-off-by: Marco Neumann <3829486b93ec44395f0b980424bae9b6fb07b7bc@crepererum.net>

inveniosoftware/invenio-base,inveniosoftware/invenio-base,tiborsimko/invenio-base,tiborsimko/invenio-base