test/sandbox: do not discard stderr getting hash

This is the first hakurei run in the test, if the container outright fails to start this is often where it happens, so throwing away the output is very unhelpful.

Signed-off-by: Ophestra <cat@gensokyo.uk>

test/sandbox/test.py

@@ -27,7 +27,7 @@ def swaymsg(command: str = "", succeed=True, type="command"):
 
 def check_filter(check_offset, name, pname):
     pid = int(machine.wait_until_succeeds(f"pgrep -U {1000000+check_offset} -x {pname}", timeout=15))
-    hash = machine.succeed(f"sudo -u alice -i XDG_RUNTIME_DIR=/run/user/1000 WAYLAND_DISPLAY=wayland-1 check-sandbox-{name} hash 2>/dev/null")
+    hash = machine.succeed(f"sudo -u alice -i XDG_RUNTIME_DIR=/run/user/1000 WAYLAND_DISPLAY=wayland-1 check-sandbox-{name} hash")
     print(machine.succeed(f"hakurei-test -s {hash} filter {pid}"))