Custom error for homebrew table not found (#1872)

Co-authored-by: seph <seph@kolide.co>

ee/allowedcmd/cmd.go

@@ -8,6 +8,7 @@ package allowedcmd
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -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: not found at %s and could not be located elsewhere", ErrCommandNotFound, knownPath)
 }
 
 func allowSearchPath() bool {

ee/tables/homebrew/upgradeable.go

@@ -6,6 +6,7 @@ package brew_upgradeable
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"log/slog"
 	"os"
@@ -43,7 +44,12 @@ func (t *Table) generate(ctx context.Context, queryContext table.QueryContext) (
 	// that user. To reduce duplicating the WithUid table helper, we can find the owner of the binary,
 	// and pass the said owner to the WIthUid method to handle setting the appropriate env vars.
 	cmd, err := allowedcmd.Brew(ctx)
+
 	if err != nil {
+		if errors.Is(err, allowedcmd.ErrCommandNotFound) {
+			// No data, no error
+			return nil, nil
+		}
 		return nil, fmt.Errorf("failure allocating allowedcmd.Brew: %w", err)
 	}