dnfjson: support redirecting dnfjsons stderr

This commit tweaks the dnfjson.Solver to also have a `Stderr`
attribute. This is a minimal change to prevent `image-builder-cli`
from showing:
```console
image-builder build qcow2 --distro centos-9 --progress=verbose
Manifest generation step
Building manifest for qcow2-centos-9
No match for group package "iwl5150-firmware"
No match for group package "iwl6050-firmware"
No match for group package "firewalld"
No match for group package "iwl7260-firmware"
No match for group package "dracut-config-rescue"
No match for group package "iwl105-firmware"
No match for group package "iwl2000-firmware"
No match for group package "iwl100-firmware"
No match for group package "iwl6000g2a-firmware"
No match for group package "iwl1000-firmware"
No match for group package "iwl3160-firmware"
No match for group package "iwl135-firmware"
No match for group package "iwl2030-firmware"
No match for group package "iwl5000-firmware"
...
```
which seems to be resulting from the "exclude" directive of the
transaction. When qcow2 in centos-9 is build it contains the following:
```go
	ps := rpmmd.PackageSet{
		Include: []string{
			"@core",
			...
		},
		Exclude: []string{
			...
			"firewalld",
			"iwl7260-firmware",
			...
		},
```
and each package that is both in @core and in the exclude seems
to trigger a message like the above, e.g.:
```
No match for group package "firewalld"
```
This is just confusing for our users so image-builder-cli will
just discard this stderr output from dnfjson.

I'm not sure if there is a better way to handle this though, ideas
(very) welcome.

pkg/dnfjson/dnfjson.go

@@ -18,6 +18,7 @@ import (
 	"crypto/sha256"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/url"
 	"os"
 	"os/exec"
@@ -154,6 +155,14 @@ type Solver struct {
 	proxy string
 
 	subscriptions *rhsm.Subscriptions
+
+	// Stderr is the stderr output from dnfjson, if unset os.Stderr
+	// will be used.
+	//
+	// XXX: ideally this would not be public but just passed via
+	// NewSolver() but it already has 5 args so ideally we would
+	// add a SolverOptions struct here with "CacheDir" and "Stderr"?
+	Stderr io.Writer
 }
 
 // DepsolveResult contains the results of a depsolve operation.
@@ -212,7 +221,7 @@ func (s *Solver) Depsolve(pkgSets []rpmmd.PackageSet, sbomType sbom.StandardType
 	s.cache.locker.RLock()
 	defer s.cache.locker.RUnlock()
 
-	output, err := run(s.dnfJsonCmd, req)
+	output, err := run(s.dnfJsonCmd, req, s.Stderr)
 	if err != nil {
 		return nil, fmt.Errorf("running osbuild-depsolve-dnf failed:\n%w", err)
 	}
@@ -266,7 +275,7 @@ func (s *Solver) FetchMetadata(repos []rpmmd.RepoConfig) (rpmmd.PackageList, err
 		return pkgs, nil
 	}
 
-	result, err := run(s.dnfJsonCmd, req)
+	result, err := run(s.dnfJsonCmd, req, s.Stderr)
 	if err != nil {
 		return nil, err
 	}
@@ -312,7 +321,7 @@ func (s *Solver) SearchMetadata(repos []rpmmd.RepoConfig, packages []string) (rp
 		return pkgs, nil
 	}
 
-	result, err := run(s.dnfJsonCmd, req)
+	result, err := run(s.dnfJsonCmd, req, s.Stderr)
 	if err != nil {
 		return nil, err
 	}
@@ -835,7 +844,7 @@ func ParseError(data []byte) Error {
 	return e
 }
 
-func run(dnfJsonCmd []string, req *Request) ([]byte, error) {
+func run(dnfJsonCmd []string, req *Request, stderr io.Writer) ([]byte, error) {
 	if len(dnfJsonCmd) == 0 {
 		dnfJsonCmd = []string{findDepsolveDnf()}
 	}
@@ -853,7 +862,11 @@ func run(dnfJsonCmd []string, req *Request) ([]byte, error) {
 		return nil, fmt.Errorf("creating stdin pipe for %s failed: %w", ex, err)
 	}
 
-	cmd.Stderr = os.Stderr
+	if stderr != nil {
+		cmd.Stderr = stderr
+	} else {
+		cmd.Stderr = os.Stderr
+	}
 	stdout := new(bytes.Buffer)
 	cmd.Stdout = stdout
 
@@ -873,6 +886,5 @@ func run(dnfJsonCmd []string, req *Request) ([]byte, error) {
 	if runError, ok := err.(*exec.ExitError); ok && runError.ExitCode() != 0 {
 		return nil, parseError(output, req.Arguments.Repos)
 	}
-
 	return output, nil
 }

pkg/dnfjson/dnfjson_test.go

@@ -858,7 +858,7 @@ exit 1
 	err := os.WriteFile(fakeDnfJsonPath, []byte(fakeDnfJsonNoOutput), 0o755)
 	assert.NoError(t, err)
 
-	_, err = run([]string{fakeDnfJsonPath}, &Request{})
+	_, err = run([]string{fakeDnfJsonPath}, &Request{}, nil)
 	assert.EqualError(t, err, `DNF error occurred: InternalError: dnf-json output was empty`)
 }
 
@@ -867,16 +867,20 @@ func TestSolverRunWithSolverNoError(t *testing.T) {
 	fakeSolver := `#!/bin/sh -e
 cat - > "$0".stdin
 echo '{"solver": "zypper"}'
+>&2 echo "output-on-stderr" 
 `
 	fakeSolverPath := filepath.Join(tmpdir, "fake-solver")
 	err := os.WriteFile(fakeSolverPath, []byte(fakeSolver), 0755) //nolint:gosec
 	assert.NoError(t, err)
 
+	var capturedStderr bytes.Buffer
 	solver := NewSolver("platform:f38", "38", "x86_64", "fedora-38", "/tmp/cache")
+	solver.Stderr = &capturedStderr
 	solver.dnfJsonCmd = []string{fakeSolverPath}
 	res, err := solver.Depsolve(nil, sbom.StandardTypeNone)
 	assert.NoError(t, err)
 	assert.NotNil(t, res)
+	assert.Equal(t, "output-on-stderr\n", capturedStderr.String())
 
 	// prerequisite check, i.e. ensure our fake was called in the right way
 	stdin, err := os.ReadFile(fakeSolverPath + ".stdin")