Use relative imports

__init__.py

@@ -1,6 +1,6 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of
 #this repository contains the full copyright notices and license terms.
 
-from party import *
-from payment_term import *
-from invoice import *
+from .party import *
+from .payment_term import *
+from .invoice import *

tests/__init__.py

@@ -1,4 +1,4 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of
 #this repository contains the full copyright notices and license terms.
 
-from test_account_invoice_history import suite
+from .test_account_invoice_history import suite