Update dnspython-2.2.0

lib/dns/_asyncbackend.py

@@ -0,0 +1,60 @@
+# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
+
+# This is a nullcontext for both sync and async.  3.7 has a nullcontext,
+# but it is only for sync use.
+
+class NullContext:
+    def __init__(self, enter_result=None):
+        self.enter_result = enter_result
+
+    def __enter__(self):
+        return self.enter_result
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        pass
+
+    async def __aenter__(self):
+        return self.enter_result
+
+    async def __aexit__(self, exc_type, exc_value, traceback):
+        pass
+
+
+# These are declared here so backends can import them without creating
+# circular dependencies with dns.asyncbackend.
+
+class Socket:  # pragma: no cover
+    async def close(self):
+        pass
+
+    async def __aenter__(self):
+        return self
+
+    async def __aexit__(self, exc_type, exc_value, traceback):
+        await self.close()
+
+
+class DatagramSocket(Socket):  # pragma: no cover
+    async def sendto(self, what, destination, timeout):
+        pass
+
+    async def recvfrom(self, size, timeout):
+        pass
+
+
+class StreamSocket(Socket):  # pragma: no cover
+    async def sendall(self, what, destination, timeout):
+        pass
+
+    async def recv(self, size, timeout):
+        pass
+
+
+class Backend:    # pragma: no cover
+    def name(self):
+        return 'unknown'
+
+    async def make_socket(self, af, socktype, proto=0,
+                          source=None, destination=None, timeout=None,
+                          ssl_context=None, server_hostname=None):
+        raise NotImplementedError