fix lint

Author: richvdh

synapse/replication/http/_base.py

@@ -22,7 +22,7 @@
 
 from prometheus_client import Counter, Gauge
 
-from synapse.api.errors import HttpResponseException, RequestSendFailed, SynapseError
+from synapse.api.errors import HttpResponseException, SynapseError
 from synapse.http import RequestTimedOutError
 from synapse.logging.opentracing import inject_active_span_byte_dict, trace
 from synapse.util.caches.response_cache import ResponseCache