AWS Secret Key for MTurkR

Question

I am trying to set up the MTurkR R package for the first time, which requires both Passkey and Passkey Secret from AWS: http://polmeth.wustl.edu/methodologist/tpm_v20_n2.pdf

However, Amazon recently "removed the ability to retrieve existing secret access keys for your AWS (root) account." see here

I tried to create an IAM user and use his passkey in the credentials() command, but get the following error:

 Error (AWS.MechanicalTurk.UnacceptableIdentity): AWS Identity and Access Management (IAM) user accounts cannot be used for Amazon Mechanical Turk. 

Is there any way around this problem? Do I need to wait for a package update?