watch_add() reports _open_osfhandle() failure with
error_setg(&error_warn, ...).  error_setg_win32(&error_warn, ...) is
undesirable just like error_setg(&error_fatal, ...) and
error_setg(&error_abort, ...) are.  Replace by warn_report().

The failure should probably be an error, but this function implements
a callback that doesn't take Error **.  I believe the failure will
make spice_server_init() fail in qemu_spice_init(), which is treated
as a fatal error.  The warning here provides more detail than the
error message there.

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 ui/spice-core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/ui/spice-core.c b/ui/spice-core.c
index 5992f9daec..7836202664 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -128,11 +128,13 @@ static void watch_update_mask(SpiceWatch *watch, int event_mask)
 static SpiceWatch *watch_add(int fd, int event_mask, SpiceWatchFunc func, void *opaque)
 {
     SpiceWatch *watch;
-
 #ifdef WIN32
+    g_autofree char *msg = NULL;
+
     fd = _open_osfhandle(fd, _O_BINARY);
     if (fd < 0) {
-        error_setg_win32(&error_warn, WSAGetLastError(), "Couldn't associate a FD with the SOCKET");
+        msg = g_win32_error_message(WSAGetLastError());
+        warn_report("Couldn't associate a FD with the SOCKET: %s", msg);
         return NULL;
     }
 #endif
-- 
2.49.0