Add tox and drone

issue4431

tests/test_timesheet_cost.py

@@ -1,6 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 import unittest
+import doctest
 import datetime
 from decimal import Decimal
 
@@ -72,7 +73,7 @@ def suite():
     suite = trytond.tests.test_tryton.suite()
     from trytond.modules.company.tests import test_company
     for test in test_company.suite():
-        if test not in suite:
+        if test not in suite and not isinstance(test, doctest.DocTestCase):
             suite.addTest(test)
     suite.addTests(unittest.TestLoader().loadTestsFromTestCase(
         TimesheetCostTestCase))