docs: function extend(errorName, customMsg) {
    // Find our error message
    for (let type in messages) {
      if (messages[type][errorName]) {
        // Extend the error message
        let origError = messages[type][errorName];
        // If origError returns multiple arguments, access the first (the error message) and append to it.
        if (_.isArray(origError())) {
          messages[type][errorName] = function() {
            let errorMessage = origError.apply(origError, arguments);
            errorMessage[0] = `${errorMessage[0]}. ${customMsg}`;
            return errorMessage;
          };
        } else {
          // Otherwise, simply append to the message.
          messages[type][errorName] = function() {
            return `${origError.apply(origError, arguments)}. ${customMsg}`;
          };
        }
        // Loggerize the message and add it to module.exports.
        module.exports[errorName] = loggerize(messages[type][errorName], type);
        return;
      }
    }
  
    // No error was found matching the name provided.
    logger.warn(`Tried to extend a nonexistent error message: ${errorName}`);
  }