[3.8] bpo-39850: Add support for abstract sockets in multiprocessing (GH-18866) (GH-18876)

(cherry picked from commit 6012f30beff7fa8396718dfb198ccafc333c565b)
diff --git a/Lib/multiprocessing/connection.py b/Lib/multiprocessing/connection.py
index c9f995e..8e2facf 100644
--- a/Lib/multiprocessing/connection.py
+++ b/Lib/multiprocessing/connection.py
@@ -102,7 +102,7 @@
         return 'AF_INET'
     elif type(address) is str and address.startswith('\\\\'):
         return 'AF_PIPE'
-    elif type(address) is str:
+    elif type(address) is str or util.is_abstract_socket_namespace(address):
         return 'AF_UNIX'
     else:
         raise ValueError('address type of %r unrecognized' % address)
@@ -597,7 +597,8 @@
         self._family = family
         self._last_accepted = None
 
-        if family == 'AF_UNIX':
+        if family == 'AF_UNIX' and not util.is_abstract_socket_namespace(address):
+            # Linux abstract socket namespaces do not need to be explicitly unlinked
             self._unlink = util.Finalize(
                 self, os.unlink, args=(address,), exitpriority=0
                 )