diff --git a/scrapy/downloadermiddlewares/httpcache.py b/scrapy/downloadermiddlewares/httpcache.py
index 495b103d1..4e06f8236 100644
--- a/scrapy/downloadermiddlewares/httpcache.py
+++ b/scrapy/downloadermiddlewares/httpcache.py
@@ -1,11 +1,19 @@
 from email.utils import formatdate
+
 from twisted.internet import defer
-from twisted.internet.error import TimeoutError, DNSLookupError, \
-        ConnectionRefusedError, ConnectionDone, ConnectError, \
-        ConnectionLost, TCPTimedOutError
+from twisted.internet.error import (
+    ConnectError,
+    ConnectionDone,
+    ConnectionLost,
+    ConnectionRefusedError,
+    DNSLookupError,
+    TCPTimedOutError,
+    TimeoutError,
+)
 from twisted.web.client import ResponseFailed
+
 from scrapy import signals
-from scrapy.exceptions import NotConfigured, IgnoreRequest
+from scrapy.exceptions import IgnoreRequest, NotConfigured
 from scrapy.utils.misc import load_object