minor fix

__init__.py

@@ -6,6 +6,7 @@ from . import party
 from . import nationality
 from . import preference
 
+
 def register():
     Pool.register(
         nationality.Nationality,

party.py

@@ -1,7 +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 datetime import datetime, date
-
+from datetime import datetime
 from trytond.i18n import gettext
 from trytond.model import fields, ModelSQL, ModelView
 from trytond.pool import PoolMeta, Pool
@@ -161,6 +160,11 @@ class PartyPreference(ModelSQL):
 class PartyByCategoryReport(Report):
     __name__ = 'party_personal.party_by_category_report'
 
+    @classmethod
+    def execute(cls, ids, data):
+        oext, content, action, filename = super(cls, PartyByCategoryReport).execute(ids, data)
+        return (oext, content, action, 'party_by_category_report')
+
     @classmethod
     def get_context(cls, records, header, data):
         Company = Pool().get('company.company')