Program run via exec and outputting to stderr assumes failure

[victorb]

Currently if you try to run a js-ipfs daemon via js-ipfsd-ctl with DEBUG set to *, ipfsd-ctl will not work correctly and assume that the js-ipfs daemon outputs errors, since the npm module debug outputs to stderr.

Rather than just seeing if there is data on stderr and fail if there is, we should save the data and output it if the exit status is not 0.

Line in question that makes the assumption:

js-ipfsd-ctl/src/utils/exec.js

Line 60 in b781fbb

command.stderr.on('data', listeners.error)

[dryajov]

Thanks @victorbjelkholm! This sounds reasonable and seems like it would fix our logging issues 👍

[achingbrain]

This should be fixed by #270