The error messages at the end of the install log mention files failing to download. I get the same kind of messages with two or three other mirrors such as those at UBC and Waterloo.
It’s difficult to see how multiple download sites could be having the same issues at the same time.
This problem is now resolved, but I still do not know why it occurred. The problem did not recur after I downed and restarted the ESXi server (and, of course, the two virtual machines on it).