migrate to upstream libcompose in one and a half go

vendor/github.com/codegangsta/cli/cli.go

@@ -17,3 +17,24 @@
 //     app.Run(os.Args)
 //   }
 package cli
+
+import (
+	"strings"
+)
+
+type MultiError struct {
+	Errors []error
+}
+
+func NewMultiError(err ...error) MultiError {
+	return MultiError{Errors: err}
+}
+
+func (m MultiError) Error() string {
+	errs := make([]string, len(m.Errors))
+	for i, err := range m.Errors {
+		errs[i] = err.Error()
+	}
+
+	return strings.Join(errs, "\n")
+}