rustdoc tests error output without tidy is very bad

[tmandry]

Note: tidy here is the html diff / format tool, not src/tools/tidy

From the 1.52 retrospective: Having this installed would have made it much easier to spot the issue in #84950.

[jyn514]

"depend" is not quite correct - tests will pass fine without it, but if they fail the error message is very bad.

[GuillaumeGomez]

We improved the error message in case tidy isn't installed to avoid showing up the HTML diff, so let's say it's less good and more difficult to understand.

[GuillaumeGomez]

I think we can close it since it's possible to run rustdoc tests without tidy installed.

[jyn514]

"depend" is not quite correct - tests will pass fine without it, but if they fail the error message is very bad.

@GuillaumeGomez this problem is still not solved.

[GuillaumeGomez]

Renaming the issue to reflect this then.

[jyn514]

@tmandry A simple solution is to just install tidy on the release builders. I don't know how to do that but it's packaged in nearly every distro.