[FIX] sale, purchase: little improvement for arguments

bzr revid: rha@tinyerp.com-20120306102405-q8etxh9kyjoyu8h6

diff --cc addons/purchase/purchase.py
index 105f71a,70c8735..3705801
--- 1/addons/purchase/purchase.py
--- 2/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@@ -676,9 -678,8 +676,9 @@@ class purchase_order_line(osv.osv)
          lang=False
          if partner_id:
              lang=self.pool.get('res.partner').read(cr, uid, partner_id, ['lang'])['lang']
-         context={'lang':lang}
-         context['partner_id'] = partner_id
- 
 -            
++        user_context = self.pool.get('res.users').context_get(cr, uid)
++        context={'lang': user_context.get('lang')}
+         context_partner = {'lang':lang, 'partner_id': partner_id}
          prod = self.pool.get('product.product').browse(cr, uid, product, context=context)
          prod_uom_po = prod.uom_po_id.id
          if not uom: