no promise error in patient search

[msmock]

The patient search throws an error, since collection.find() returns no promise. The problem is solved with replacing the search function with:

module.exports.search = (args) =>

new Promise((resolve, reject) => {

logger.info('Patient >>> search');

let { base_version } = args;
let query = {};

switch (base_version) {
  case VERSIONS['1_0_2']:
    query = buildDstu2SearchQuery(args);
    break;
  case VERSIONS['3_0_1']:
  case VERSIONS['4_0_0']:
  case VERSIONS['4_0_1']:
    query = buildStu3SearchQuery(args);
    break;
}

// Grab an instance of our DB and collection
let db = globals.get(CLIENT_DB);
let collection = db.collection(`${COLLECTION.PATIENT}_${base_version}`);
let Patient = getPatient(base_version);

// Query our collection for this observation
collection
  .find(query)
  .toArray()
  .then((patients) => {
    // convert mongo object to fhir ressource
    patients.forEach(function (element, i, returnArray) {
      returnArray[i] = new Patient(element);
    });
    resolve(patients);
  })
  .catch((err) => {
    logger.error('Error with Patient.search: ', err);
    return reject(handleError({ error: err }));
  });

});