As initially brought up in https://github.com/datalad/datalad/pull/2515#issuecomment-391022075 it would be nice if there was a clear/robust way to programmatically obtain information why `enableremote` failed

May be even more generally -- if there was a robust way to obtain errors for other commands as well, e.g. such as `fatal` messages such as `this operation must be run in a work tree`

[[!meta author=yoh]]
[[!tag projects/datalad]]
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