Too short error messages

[maleadt]

Sandbox.jl's error message are really dense, and sometimes nearly unusable.

At line 283, ABORTED (2: No such file or directory)!

Turned out /proc didn't exist.

At line 139, ABORTED (2: No such file or directory)!

Impossible to actually find out what was wrong; touch failed but the argument isn't reported.
Turned out /dev didn't exist.

Verbose mode often helps, but I'd argue some additional error information would be valuable too.

[vtjnash]

Appears fixed by #87 a year ago, but no release since?