callProcess exception undocumented

The docs say that callProcess throws an exception when the process returns non-zero. It is not documented what type of exception this is and therefore this API is pretty much useless. Please consider documenting the exception type or adding a new API that returns the status code instead.

Start by locating the callProcess API documentation and its implementation or related tests. Confirm the exception behavior and document the exception type, or clarify the supported status-code alternative; done means callers can identify how non-zero process exits are reported.

Written by the indexing model from the issue text.