Handle network errors with better messaging

[ecooper]

Problem

When a network error occurs in the v10 driver, we get a "The network encountered a problem" message. If fetch fails, you get a "fetch failed". Neither of these are helpful.

Solution

Catch them with slightly better messaging and centralize the messaging so we are consistent in the places we need to handle these errors. Given the most likely cause of a network error is --local, add a blurb about that too.

All commands are covered by this messaging, but may display them differently depending on their error handling.

Result

Testing

Unit tests.

[jrodewig]

LGTM. Left some message nits you can take or leave as you see fit.