Resolve warnings from modern flake8

src/pretix/control/templatetags/order_overview.py

@@ -8,12 +8,15 @@ register = template.Library()
 
 @register.filter(name='togglesum', needs_autoescape=True)
 def cut(value, autoescape=True):
+    def noop(x):
+        return x
+
     if not value:
         return ''
     if autoescape:
         esc = conditional_escape
     else:
-        esc = lambda x: x
+        esc = noop
     return mark_safe('<span class="count">{0}</span><span class="sum">{1}</span>'.format(
         esc(value[0]), esc(formats.localize(value[1]))
     ))