feat: add error tracing

[zyllee]

Prerequisite checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Ran make fmt on your commit series before opening this PR;
• Updated relevant documentation.

Description of changes

To add the feature related to #34.
The juju package for error handling is currently imported. Wrote the test code.

[nderjung]

Hi @zyllee, thanks for this contribution!

The issue you've addressed is out-of-date in terms of its implementation but not its requirements. We have since added internal/errs to KraftKit which now stores error types (instead of iota/ints, they're strings).

As discussed on Discord, the need for a error tracing system is still required and juju's errors module still seems like a good fit.

Based on the juju errors' README, you would technically need to use the juju errors package to replace the internal package's definition of errors with juju's, i.e.:

index 8206a12..4d88304 100644
--- a/internal/errs/defs.go
+++ b/internal/errs/defs.go
@@ -4,7 +4,9 @@
 // You may not use this file expect in compliance with the License.
 package errs

-import "errors"
+import
+       "github.com/juju/errors"
+)

However, we actually do NOT need to replace the above, in fact, since internal/errs declares the same (subset) of errors, this can be removed since they will be duplicate. Only when we add new error types (which is possible), would we need to restore this package with custom definitions. Let's hold off for now and simply remove this package.

Instead, to continue this work, I would recommend going through the KraftKit source code and replacing all instances of return fmt.Errorf and errors.New with valid juju errors wrappers. This will allow us to a). classify each error into a category and b). allow us to unwrap each error nicely since the system will homogenise. The moment where errors are actually printed to the console occurs in cmdfactory.Main:

kraftkit/cmdfactory/builder.go

Lines 175 to 184 in 06bef51

	// Main executes the given command
	func Main(ctx context.Context, cmd *cobra.Command) {
	// Expand flag all dynamically registered flag overrides.
	expandRegisteredFlags(cmd)
	if err := cmd.ExecuteContext(ctx); err != nil {
	fmt.Println(err)
	os.Exit(1)
	}
	}

Replace fmt.Printf(err) with errors.ErrorStack(err)

For the first iteration on your side, this needs to be replace with juju errors' Unwrap or Trace method which will output the call stack or the list of errors which have occurred.

Finally, the code related to "user" look up can be removed entirely since this is out-of-scope of the project.

[zyllee]

The screenshots above(except the first one) are running in cmd kraft build --arch x86_64 --plat kvm. I test it by changing if condition to satisfied return error to happen.

[nderjung]

Closing due to age and it requiring a large rebase.