yes i created the file manually and i checked the permissions the are set for read & write to all users , this is the function inside models.py

# -*- coding: utf-8 -*-

from datetime import timedelta, date, datetime

import pytz

from openerp import models, fields, api, _, tools
from openerp.exceptions import Warning
from openerp.osv import osv, fields, orm

from pyimppn import imppn_line
import psycopg2
import os

import logging
_logger = logging.getLogger(__name__)

class companyimppn(models.Model):
    _inherit = 'res.company'

    x_teamsystemid = fields.integer(string='Teamsystem id')

class view(osv.osv):
    _inherit = ['ir.ui.view']

    def __init__(self, pool, cr):
        super(view, self).__init__(pool, cr)
        super(view, self)._columns['type'].selection.append(('odooimppnview','OdooimppnView'))
 
class odooimppn(models.Model):
    _name = 'odoo_imppn.content'
    _description = 'Odoo imppn content'


    def testing(self):
        results = "this is a test to see if we are able to write on a text file located inside the module"
        path = os.path.expanduser('./etc/odoo/addons/odoo_imppn/IMPPN_tests.txt')
        # path = os.path.expanduser('./home/mounirlahsini/Downloads/IMPPN_tests.txt')
        fileIMPPN = open(path, 'r+')
        fileIMPPN.write(results)
        fileIMPPN.close()

testing()