misc: fix dangerous-default-value pylint error (#56288)

combo/utils/cache.py

@@ -18,6 +18,7 @@ from combo.middleware import get_request
 
 
 # _make_key and _HashedSeq imported/adapted from functools from Python 3.2+
+# pylint: disable=dangerous-default-value
 def _make_key(
     args,
     kwds,

combo/utils/signature.py

@@ -55,7 +55,8 @@ def sign_string(s, key, algo='sha256', timedelta=30):
     return hash.digest()
 
 
-def check_request_signature(django_request, keys=[]):
+def check_request_signature(django_request, keys=None):
+    keys = keys or []
     query_string = django_request.META['QUERY_STRING']
     if not query_string:
         return False