PEP fixes

InvenTree/InvenTree/models.py

@@ -7,7 +7,6 @@ from __future__ import unicode_literals
 from django.db import models
 from django.contrib.contenttypes.models import ContentType
 from rest_framework.exceptions import ValidationError
-from .helpers import str2bool
 
 from django.db.models.signals import pre_delete
 from django.dispatch import receiver

InvenTree/build/models.py

@@ -55,7 +55,6 @@ class Build(models.Model):
     batch = models.CharField(max_length=100, blank=True, null=True,
                              help_text='Batch code for this build output')
 
-
     #: Date the build model was 'created'
     creation_date = models.DateField(auto_now=True, editable=False)