[dataimport] fix db-namespace default value handling
In a fresh new instance, the "db-namespace" option is set as empty
by default in the "sources" file.
This seems correct but empty string is not a valid pg_schema and
actually means that we should use "public"
.. _web_module:
:mod:`cubicweb.web`
===================
.. automodule:: cubicweb.web
Exceptions
----------
.. autoexception:: DirectResponse
.. autoexception:: InvalidSession
.. autoexception:: PublishException
.. autoexception:: LogOut
.. autoexception:: Redirect
.. autoexception:: StatusResponse
.. autoexception:: RequestError
.. autoexception:: NothingToEdit
.. autoexception:: ProcessFormError
.. autoexception:: NotFound
.. autoexception:: RemoteCallFailed