2 files changed, 55 insertions, 10 deletions

diff --git a/tests/qemu-iotests/257 b/tests/qemu-iotests/257
index fb5359c..e7e7a23 100755
--- a/tests/qemu-iotests/257
+++ b/tests/qemu-iotests/257
@@ -241,11 +241,13 @@ def compare_images(image, reference, baseimg=None, expected_match=True):
     expected_ret = 0 if expected_match else 1
     if baseimg:
         qemu_img("rebase", "-u", "-b", baseimg, '-F', iotests.imgfmt, image)
-    ret = qemu_img("compare", image, reference)
+
+    sub = qemu_img("compare", image, reference, check=False)
+
     log('qemu_img compare "{:s}" "{:s}" ==> {:s}, {:s}'.format(
         image, reference,
-        "Identical" if ret == 0 else "Mismatch",
-        "OK!" if ret == expected_ret else "ERROR!"),
+        "Identical" if sub.returncode == 0 else "Mismatch",
+        "OK!" if sub.returncode == expected_ret else "ERROR!"),
         filters=[iotests.filter_testfiles])
 
 def test_bitmap_sync(bsync_mode, msync_mode='bitmap', failure=None):
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 508adad..4afe63d 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -37,9 +37,10 @@ import unittest
 
 from contextlib import contextmanager
 
+from qemu.aqmp.legacy import QEMUMonitorProtocol
 from qemu.machine import qtest
 from qemu.qmp import QMPMessage
-from qemu.aqmp.legacy import QEMUMonitorProtocol
+from qemu.utils import VerboseProcessError
 
 # Use this logger for logging messages directly from the iotests module
 logger = logging.getLogger('qemu.iotests')
@@ -215,9 +216,50 @@ def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
     return qemu_tool_pipe_and_status('qemu-img', full_args,
                                      drop_successful_output=is_create)
 
-def qemu_img(*args: str) -> int:
-    '''Run qemu-img and return the exit code'''
-    return qemu_img_pipe_and_status(*args)[1]
+def qemu_img(*args: str, check: bool = True, combine_stdio: bool = True
+             ) -> 'subprocess.CompletedProcess[str]':
+    """
+    Run qemu_img and return the status code and console output.
+
+    This function always prepends QEMU_IMG_OPTIONS and may further alter
+    the args for 'create' commands.
+
+    :param args: command-line arguments to qemu-img.
+    :param check: Enforce a return code of zero.
+    :param combine_stdio: set to False to keep stdout/stderr separated.
+
+    :raise VerboseProcessError:
+        When the return code is negative, or on any non-zero exit code
+        when 'check=True' was provided (the default). This exception has
+        'stdout', 'stderr', and 'returncode' properties that may be
+        inspected to show greater detail. If this exception is not
+        handled, the command-line, return code, and all console output
+        will be included at the bottom of the stack trace.
+
+    :return:
+        a CompletedProcess. This object has args, returncode, and stdout
+        properties. If streams are not combined, it will also have a
+        stderr property.
+    """
+    full_args = qemu_img_args + qemu_img_create_prepare_args(list(args))
+
+    subp = subprocess.run(
+        full_args,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT if combine_stdio else subprocess.PIPE,
+        universal_newlines=True,
+        check=False
+    )
+
+    if check and subp.returncode or (subp.returncode < 0):
+        raise VerboseProcessError(
+            subp.returncode, full_args,
+            output=subp.stdout,
+            stderr=subp.stderr,
+        )
+
+    return subp
+
 
 def ordered_qmp(qmsg, conv_keys=True):
     # Dictionaries are not ordered prior to 3.6, therefore:
@@ -232,7 +274,7 @@ def ordered_qmp(qmsg, conv_keys=True):
         return od
     return qmsg
 
-def qemu_img_create(*args):
+def qemu_img_create(*args: str) -> 'subprocess.CompletedProcess[str]':
     return qemu_img('create', *args)
 
 def qemu_img_measure(*args):
@@ -467,8 +509,9 @@ def qemu_nbd_popen(*args):
 
 def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
     '''Return True if two image files are identical'''
-    return qemu_img('compare', '-f', fmt1,
-                    '-F', fmt2, img1, img2) == 0
+    res = qemu_img('compare', '-f', fmt1,
+                   '-F', fmt2, img1, img2, check=False)
+    return res.returncode == 0
 
 def create_image(name, size):
     '''Create a fully-allocated raw image with sector markers'''