iotests.py: Do not wait() before communicate()

Waiting on a process for which we have a pipe will stall if the process
outputs more data than fits into the OS-provided buffer.  We must use
communicate() before wait(), and in fact, communicate() perfectly
replaces wait() already.

We have to drop the stderr=subprocess.STDOUT parameter from
subprocess.Popen() in qemu_nbd_early_pipe(), because stderr is passed on
to the child process, so if we do not drop this parameter, communicate()
will hang (because the pipe is not closed).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200630083711.40567-1-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

0 files changed, 0 insertions, 0 deletions