How to expect error with given class and capture message?

[hadley]

If you want to carefully check that an function yields an error with the expected class and capture the human readable message, you need something like this:

expect_snapshot({
  (expect_error(foo(), class = "bar"))
})

Could we turn this into a more concise assertion either by including the code in the output of expect_snapshot_error(), or if that's too disruptive to existing code, by adding a new expect_error_snapshot()?

Related to #1471

[hadley]

Need doesn't great anymore, so I'm going to close.