Skip test_socket.test_sha256() on linux < 4.5 (#4643)

bpo-31705.

Lib/test/test_socket.py

@@ -5573,6 +5573,9 @@ class LinuxKernelCryptoAPI(unittest.TestCase):
         else:
             return sock
 
+    # bpo-31705: On kernel older than 4.5, sendto() failed with ENOKEY,
+    # at least on ppc64le architecture
+    @support.requires_linux_version(4, 5)
     def test_sha256(self):
         expected = bytes.fromhex("ba7816bf8f01cfea414140de5dae2223b00361a396"
                                  "177a9cb410ff61f20015ad")

Misc/NEWS.d/next/Tests/2017-11-30-12-27-10.bpo-31705.yULW7O.rst

+Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test
+fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the
+kernel 4.5.