Byte string doesn't have a format function in python 3

lms/djangoapps/shoppingcart/tests/test_reports.py

@@ -108,11 +108,11 @@ class ReportTypeTests(ModuleStoreTestCase):
         second_refund.refund_requested_time = self.test_time
         second_refund.save()
 
-        self.CORRECT_REFUND_REPORT_CSV = dedent(b"""
+        self.CORRECT_REFUND_REPORT_CSV = dedent(u"""
             Order Number,Customer Name,Date of Original Transaction,Date of Refund,Amount of Refund,Service Fees (if any)
             3,King Bowsér,{time_str},{time_str},40.00,0.00
             4,Súsan Smith,{time_str},{time_str},40.00,0.00
-            """.format(time_str=str(self.test_time)))
+            """.format(time_str=str(self.test_time))).encode('utf-8')
 
         self.CORRECT_CERT_STATUS_CSV = dedent("""
             University,Course,Course Announce Date,Course Start Date,Course Registration Close Date,Course Registration Period,Total Enrolled,Audit Enrollment,Honor Code Enrollment,Verified Enrollment,Gross Revenue,Gross Revenue over the Minimum,Number of Verified Students Contributing More than the Minimum,Number of Refunds,Dollars Refunded