use unidecode to get around stupid unicode problem in invoice worker log

requirements/base.txt

@@ -9,3 +9,4 @@ Pillow==3.2.0
 qrcode==5.3
 CommonMark==0.6.4
 django-bleach==0.3.0
+Unidecode==0.4.19

shop/models.py

@@ -10,7 +10,7 @@ from django.utils import timezone
 from django.core.urlresolvers import reverse_lazy
 from utils.models import UUIDModel, CreatedUpdatedModel
 from .managers import ProductQuerySet, OrderQuerySet
-import hashlib, io, base64, qrcode
+import hashlib, io, base64, qrcode, unidecode
 from decimal import Decimal
 from datetime import timedelta
 
@@ -379,7 +379,7 @@ class Invoice(CreatedUpdatedModel):
                 self.customorder.id,
                 self.customorder.created,
                 self.customorder.amount,
-                self.customorder.customer,
+                unidecode(self.customorder.customer),
             )
 
     @property