And add error message to hint if the problem is that the passed binary
path is not absolute or if the binary doesn't exist.

In case the PID is correct:

* but the binary couldn't be found, it will print:

  ```
  HINT: Specified binary doesn't exist.
  [...]
  ```

* but the binary is not absolute:

  ```
  HINT: Binary path should be absolute.
  [...]
  ```

Otherwise, it should keep behaving as before.