Option for skipping auth failures in addition to connection ones

[bitprophet]

In #8 we added the ability to skip over connection failures (née NetworkError) but left authentication issues as a hard abort() since that's a different "class" of problem that felt like it should continue to fail-fast.

However, we should eventually update things to let users who know what they're doing opt-in to skipping over those as well, probably with a similar approach (use the exceptions-for machinery, and another setting that can be toggled at CLI or fabric.env level, so they can either catch an exception or set a flag.)

[bitprophet]

Possibly related to #714

[prune998]

maybe an env variable like "continue_on_prompt" instead of "abort_on_prompt" ?

[th3penguinwhisperer]

I'm looking exactly at this feature. Need it for large scale cloud deployments.
Any ETA on this? :) Or where I can modify this in the code to prevent this abort?
I need password auth for setting up the keys first. However if that password fails it should go on to the next one instead of keep asking for the password.
And the abort stops the whole run :(