Custom error for command not found

ee/allowedcmd/cmd.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"errors"
 )
 
 type AllowedCommand func(ctx context.Context, arg ...string) (*exec.Cmd, error)
@@ -20,6 +21,8 @@ func newCmd(ctx context.Context, fullPathToCmd string, arg ...string) *exec.Cmd
 	return exec.CommandContext(ctx, fullPathToCmd, arg...) //nolint:forbidigo // This is our approved usage of exec.CommandContext
 }
 
+var ErrCommandNotFound = errors.New("command not found")
+
 func validatedCommand(ctx context.Context, knownPath string, arg ...string) (*exec.Cmd, error) {
 	knownPath = filepath.Clean(knownPath)
 
@@ -31,15 +34,15 @@ func validatedCommand(ctx context.Context, knownPath string, arg ...string) (*ex
 	// We expect to know the exact location for allowlisted commands on all
 	// OSes except for a few Linux distros.
 	if !allowSearchPath() {
-		return nil, fmt.Errorf("not found: %s", knownPath)
+		return nil, fmt.Errorf("%w: %s",ErrCommandNotFound, knownPath)
 	}
 
 	cmdName := filepath.Base(knownPath)
 	if foundPath, err := exec.LookPath(cmdName); err == nil {
 		return newCmd(ctx, foundPath, arg...), nil
 	}
 
-	return nil, fmt.Errorf("%s not found at %s and could not be located elsewhere", cmdName, knownPath)
+	return nil, fmt.Errorf("%w: %s and could not be located elsewhere", ErrCommandNotFound, knownPath)
 }
 
 func allowSearchPath() bool {

ee/allowedcmd/cmd_linux.go

@@ -13,12 +13,10 @@ func Apt(ctx context.Context, arg ...string) (*exec.Cmd, error) {
 	return validatedCommand(ctx, "/usr/bin/apt", arg...)
 }
 
-var ErrHomebrewNotFound = errors.New("homebrew not found")
-
 func Brew(ctx context.Context, arg ...string) (*exec.Cmd, error) {
 	validatedCmd, err := validatedCommand(ctx, "/home/linuxbrew/.linuxbrew/bin/brew", arg...)
 	if err != nil {
-		return nil, ErrHomebrewNotFound
+		return nil, nil
 	}
 
 	validatedCmd.Env = append(validatedCmd.Environ(), "HOMEBREW_NO_AUTO_UPDATE=1")

ee/tables/homebrew/upgradeable.go

@@ -46,7 +46,7 @@ func (t *Table) generate(ctx context.Context, queryContext table.QueryContext) (
 	cmd, err := allowedcmd.Brew(ctx)
 
 	if err != nil {
-		if errors.Is(err, allowedcmd.ErrHomebrewNotFound) {
+		if errors.Is(err, allowedcmd.ErrCommandNotFound) {
 			// No data, no error
 			return nil, nil
 		}