How to use the pouchdb-utils.explainError function in pouchdb-utils

setupPromise = fetchJSON(dbUrl).catch(function (err) {
      if (err && err.status && err.status === 404) {
        // Doesnt exist, create it
        explainError(404, 'PouchDB is just detecting if the remote exists.');
        return fetchJSON(dbUrl, {method: 'PUT'});
      } else {
        return Promise.reject(err);
      }
    }).catch(function (err) {
      // If we try to create a database that already exists, skipped in

doBulkGet(function (err, res) {
        if (err) {
          supportsBulkGetMap[dbUrl] = false;
          explainError(
            err.status,
            'PouchDB is just detecting if the remote ' +
            'supports the _bulk_get API.'
          );
          doBulkGetShim();
        } else {
          supportsBulkGetMap[dbUrl] = true;
          callback(null, res);
        }
      });
    } else if (supportsBulkGet) {

return db.get(id).catch(function (err) {
    if (err.status === 404) {
      if (db.adapter === 'http' || db.adapter === 'https') {
        explainError(
          404, 'PouchDB is just checking if a remote checkpoint exists.'
        );
      }
      return {
        session_id: session,
        _id: id,
        history: [],
        replicator: REPLICATOR,
        version: CHECKPOINT_VERSION
      };
    }
    throw err;
  }).then(function (doc) {
    if (returnValue.cancelled) {

return db.get(id).catch(function (err) {
    if (err.status === 404) {
      if (db.adapter === 'http' || db.adapter === 'https') {
        explainError(
          404, 'PouchDB is just checking if a remote checkpoint exists.'
        );
      }
      return {
        session_id: session,
        _id: id,
        history: [],
        replicator: REPLICATOR,
        version: CHECKPOINT_VERSION
      };
    }
    throw err;
  }).then(function (doc) {
    if (returnValue.cancelled) {