Missing context in install output when post-install file writing fails

[vzsg]

While trying to work around #348, I tried directing the post-install file to /dev/null, which is apparently working in Docker but not allowed everywhere, particularly in a Heroku buildpack¹. The reason I'm opening this issue is about the way the permission error was presented.

This is an excerpt of the output of swiftly install 6.0.3 --use --post-install-file /dev/null --verbose, executed by the buildpack:

remote: /app/.local/share/swiftly/toolchains/6.0.3/usr/share/swift/LICENSE.txt
remote: Setting up toolchain proxies...
remote: The file `file:///tmp/codon/tmp/buildpacks/478529ceede3913b5933458f7612f2e8d52d73ac/.swift-version` has been set to `Swift 6.0.3`
remote: The global default toolchain has been set to `Swift 6.0.3`
remote: Swift 6.0.3 installed successfully!
remote: NOTE: We have updated some elements in your path and your shell may not yet be
remote: aware of the changes. You can run this command to update your shell.
remote: 
remote:     hash -r
remote: Error: Error Domain=NSCocoaErrorDomain Code=513 "You don’t have permission."
[...standard Heroku build failure redacted...]

It would have been nice if there was some context, e.g. that the permission error came from saving the post-install file, at least in the verbose output. And maybe if it all went down before telling me that installation was successful².

Footnotes

1. It was an act out of desperation and is not that important here. ↩

2. Task failed successfully. /s ↩