Causal error messages are not great!

[brson]

brian@DESKTOP-CODN6ST MINGW64 /c/Users/brian/Documents/dev/taskcluster-crater/rs
$ rustup update stable
info: syncing channel updates for 'stable-x86_64-pc-windows-msvc'
info: downloading component 'rustc'
info: downloading component 'rust-std'
info: downloading component 'cargo'
info: downloading component 'rust-std' for 'armv7-apple-ios'
info: downloading component 'rust-std' for 'i686-apple-darwin'
error: component download failed for rust-std-i686-apple-darwin
info: caused by: could not download file from 'https://static.rust-lang.org/dist/2017-03-11/rust-std-1.16.0-i686-apple-darwin.tar.gz' to 'C:\Users\brian\.rustup\tmp\4y0bss25meytiiyq_file
info: caused by: error during download
info: caused by: [18] Transferred a partial file (transfer closed with 3544136 bytes remaining to read)

Here it's on the 4th line back that we're told there's an error. All subsequent lines just claim to be 'info', and the info lines contain double-colons!

This needs some custom formatting that clearly indicates all this is error stuff.

[ecumene]

I'd like to contribute!

I'm confused by what OP means by "and the info lines contain double-colons!", how should these messages be rendered? Something like this?

error caused by: could not download file from 'https://static.rust-lang.org/dist/2017-03-11/rust-std-1.16.0-i686-apple-darwin.tar.gz' to 'C:\Users\brian\.rustup\tmp\4y0bss25meytiiyq_file
error caused by: caused by: error during download
error caused by: [18] Transferred a partial file (transfer closed with 3544136 bytes remaining to read)

[kinnison]

The prefix: caused by: continuation form isn't beautiful, but I'm not sure what'd be nicer.