func (v ServerNotInstalledError) Error() string {
	return fmt.Sprintf("server for %#q VCS is not installed", v.name)
}

// HandleScript ensures that the script at scriptRelPath has been evaluated
// with its current contents.
//
// If the script completed successfully, HandleScript invokes f on the handler
// with the script's result still read-locked, and waits for it to return. (That