The patch looks good. I only have one question:

Why are you removing this part ? ...

@@ -1684,13 +1688,8 @@
             try:
                 ret = func(*args)
             except ssl.SSLError as e:
-                # Note that we get a spurious -1/SSL_ERROR_SYSCALL for
-                # non-blocking IO. The SSL_shutdown manpage hints at this.
-                # It *should* be safe to just ignore SYS_ERROR_SYSCALL because
-                # with a Memory BIO there's no syscalls (for IO at least).
                 if e.errno not in (ssl.SSL_ERROR_WANT_READ,
-                                   ssl.SSL_ERROR_WANT_WRITE,
-                                   ssl.SSL_ERROR_SYSCALL):
+                                   ssl.SSL_ERROR_WANT_WRITE):
                     raise
                 errno = e.errno
             # Get any data from the outgoing BIO irrespective of any error, and