`pycriu` doesn't receive `cr_errmsg` with `use_binary`

[herheliuk]

criu/criu/log.c

Line 147 in ae971c9

char *log_first_err(void)

^ function that returns NULL here:

criu/criu/cr-service.c

Line 141 in ae971c9

resp->cr_errmsg = log_first_err();

So if you add print(resp.cr_errmsg) here:

criu/lib/pycriu/criu.py

Lines 291 to 292 in ae971c9

	if not resp.success:
	raise CRIUExceptionExternal(req.type, resp.type, resp.cr_errno)

the output is empty:

[herheliuk]

turn out print(resp.cr_errmsg) does have a valid string when using use_sk:

Error (criu/cr-service.c:335): Can't open images directory: No such file or directory

[herheliuk]

This issue prevents a better solution for #2802.

[github-actions]

A friendly reminder that this issue had no activity for 30 days.