Comment 1 for bug 750274

This seems like a genuine bug in the Librarian, and I suspect will be causing uploads to randomly fail on production too. Do we see them in the OOPS reports?

_checkError sees the socket still has data to be read, but when it looks, the data that awaits is a success code. The Librarian is emitting a success code when one is not expected, and normally this passes because the check is made immediately after sending information to the Librarian and the Librarian will have normally not had time yet to process the information and respond.