fix #158 issue with error message with mocha connector
fix #158 issue with error message with mocha connector

Error messages do not seem to be correctly sent on PhantomJS 2.x when
using the mocha connector. This commit fixes this issue.

attester/attester,attester/attester,attester/attester,divdavem/attester,divdavem/attester,divdavem/attester