ShoppingCart: Added number receipt to PDF name file

lms/djangoapps/shoppingcart/models.py

@@ -409,7 +409,7 @@ class Order(models.Model):
                 if csv_file:
                     email.attach(u'RegistrationCodesRedemptionUrls.csv', csv_file.getvalue(), 'text/csv')
                 if pdf_file is not None:
-                    email.attach(u'Receipt.pdf', pdf_file.getvalue(), 'application/pdf')
+                    email.attach(u'Receipt{}.pdf'.format(str(self.id)), pdf_file.getvalue(), 'application/pdf')
                 else:
                     file_buffer = StringIO.StringIO(_('pdf download unavailable right now, please contact support.'))
                     email.attach(u'pdf_not_available.txt', file_buffer.getvalue(), 'text/plain')