PEP style fixes

InvenTree/build/models.py

@@ -725,7 +725,6 @@ class Build(MPTTModel, ReferenceIndexingMixin):
                                     install_into=output,
                                 )
 
-
         else:
             """
             Create a single build output of the given quantity

InvenTree/build/views.py

@@ -6,16 +6,14 @@ Django views for interacting with Build objects
 from __future__ import unicode_literals
 
 from django.utils.translation import ugettext_lazy as _
-from django.core.exceptions import ValidationError
 from django.views.generic import DetailView, ListView
-from django.forms import HiddenInput
 
 from .models import Build
 from . import forms
 
 from InvenTree.views import AjaxUpdateView, AjaxDeleteView
 from InvenTree.views import InvenTreeRoleMixin
-from InvenTree.helpers import str2bool, extract_serial_numbers
+from InvenTree.helpers import str2bool
 from InvenTree.status_codes import BuildStatus