Improve error message when binary is not found

[Kobzol]

When you start a program that does not exist, HQ shows the error in hq job info last, but nothing is included in the stdout/stderr files of the tasks. Maybe we could add this error also to stderr, to make it easier to figure out what went wrong.

[spirali]

I do not think this is a good idea. HQ commands should be a ground truth for task status. Stdout/Stderr is something produced by the task and we should not interfere with this.

[Kobzol]

We could give a very explicit annotation that the content was generated by HQ, or create a separate file on disk with this error. Sometimes people just take a look at stdout/stderr and expect to see everything there (which is mostly how PBS/Slurm works). In HQ, you also need to examine the job status to see the details.

[spirali]

There are still errors that cannot be solved like this, e.g. task fails because its dependency fail. Or task fails because worker cannot create a stderr because of permissions. So it cannot be universal, and having semantics "sometimes you will find error from HQ in stderr and sometimes not, is worse than the current situation.

[spirali]

When thinking more about it. If we promise output solely for this particular error, it should be ok.