title: Unable to import invoice data from .csv file
body: <p>I have some invoice data in openerp 7, exported it and tried to import it in odoo 8 through csv format.Partner_id is defined but still I am getting this error,</p>
  
  <pre><code>No matching record found for external id '__export__.account_account_8' in field 'Account' between rows 2 and 3
  No matching record found for external id '__export__.account_journal_1' in field 'Journal' between rows 2 and 3
  No matching record found for external id '__export__.res_partner_5' in field 'Partner' between rows 2 and 3
  No matching record found for external id '__export__.account_invoice_line_3' in field 'Invoice Lines' between rows 2 and 3
  Missing required value for the field 'Partner' (partner_id) between rows 2 and 3
  IntegrityError: null value in column "partner_id" violates not-null constraint
  </code></pre>