It will appear only when 'login' field is blank/not given in file.

Thanks,

Thanks you Prakash for list of mandatory fields,  

Here is my full xml sample :

    <record id="myuser" model="res.users">

         <field name="name">myuser bla bla</field>

         <field name="login">myuser_bla_bla</field> 

         <field name="partner_id" eval="ref('base.main_partner')"/> <!-- base.main_partner is the external id of a res_partner -->

         <field name="comment">User for my website interface</field> 

          <field name="groups_id" eval="[(4, ref('mymodule.mypublicgroup')) ]"/> <!-- mymodule.mypublicgroup is the external id of a res_group to give some rights to my new user -->

    </record>

+1

I just got into the very same error!

In my case I just added some dummy data and create two user accounts first from the interface level and then I export those in to an excel sheet by using export button in Tree-view. Then again I created my csv file according to that file and then Import it again without any error.

Can you try with a fresh database without demo data? Demo data from some module may be causing the error. I think you may find the error causing file from the error log.

Prakash's answer works for me. To import users from cvs/xls file just need minimum two fields: Name and Login (email).