What does file-error mean as network process status?

[emacsq]

Some of my url-retrieve processes got stuck and when I did an
M-x list-processes, it listed them with the status: file-error

What does file-error mean here? The process-status doc does
not list such a status:

The returned value is one of the following symbols:

run -- for a process that is running.
stop -- for a process stopped but continuable.
exit -- for a process that has exited.
signal -- for a process that has got a fatal signal.
open -- for a network stream connection that is open.
listen -- for a network stream server that is listening.
closed -- for a network stream connection that is closed.
connect -- when waiting for a non-blocking connection to complete.
failed -- when a non-blocking connection has failed.
nil -- if arg is a process name and no such process exists.
PROCESS may be a process, a buffer, the name of a process, or
nil, indicating the current buffer's process.

For a network, serial, or pipe connection, ‘process-status’ returns
one of the symbols ‘open’, ‘stop’, or ‘closed’. The latter means
that the other side closed the connection, or Emacs did
‘delete-process’. The value ‘stop’ means that ‘stop-process’ was
called on the connection.