Skip network tests when getaddrinfo() returns EAI_AGAIN, meaning a temporary
failure in name resolution.

Should fix a buildbot failure.
diff --git a/Lib/test/support.py b/Lib/test/support.py
index 83ea6c1..e2d7ae0 100644
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -867,6 +867,7 @@
         ('ETIMEDOUT', 110),
     ]
     default_gai_errnos = [
+        ('EAI_AGAIN', -3),
         ('EAI_NONAME', -2),
         ('EAI_NODATA', -5),
         # Encountered when trying to resolve IPv6-only hostnames