tests: redirect stderr to stdout for iotests

The python I/O tests helper for running qemu-img/qemu-io
setup stdout to be captured to a pipe, but left stderr
untouched. As a result, if something failed in qemu-img/
qemu-io, data written to stderr would get output directly
and not line up with data on the test stdout due to
buffering.  If we explicitly redirect stderr to the same
pipe as stdout, things are much clearer when they go
wrong.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 0a238ec1b7..5f82bbe23a 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -71,7 +71,9 @@ def qemu_img_verbose(*args):
 
 def qemu_img_pipe(*args):
     '''Run qemu-img and return its output'''
-    subp = subprocess.Popen(qemu_img_args + list(args), stdout=subprocess.PIPE)
+    subp = subprocess.Popen(qemu_img_args + list(args),
+                            stdout=subprocess.PIPE,
+                            stderr=subprocess.STDOUT)
     exitcode = subp.wait()
     if exitcode < 0:
         sys.stderr.write('qemu-img received signal %i: %s\n' % (-exitcode, ' '.join(qemu_img_args + list(args))))
@@ -80,7 +82,8 @@ def qemu_img_pipe(*args):
 def qemu_io(*args):
     '''Run qemu-io and return the stdout data'''
     args = qemu_io_args + list(args)
-    subp = subprocess.Popen(args, stdout=subprocess.PIPE)
+    subp = subprocess.Popen(args, stdout=subprocess.PIPE,
+                            stderr=subprocess.STDOUT)
     exitcode = subp.wait()
     if exitcode < 0:
         sys.stderr.write('qemu-io received signal %i: %s\n' % (-exitcode, ' '.join(args)))