Unnecessarily ambiguous to me, and probably force a hash in credentials that could be different that the program expects. Are we sure that "user" is the key for "password"? ( or maybe the "fourth element in the list credentials" is the key for password? and "user" is the value for "the third element in the list credentials", or maybe the third element in the list has "password" as username? )
I'm not saying that this is how the module works internally, I don't know, but taking a look to the source in order to discard or confirm this could help. After the question it seems to me that credentials are not parsing accurately for any reason, so OP probably want to change this fat comma and try again.