[PATCH 04/19] iotests.py: Add qemu_img_pipe_and_status()

[Max Reitz <mreitz@redhat.com>]

This function will be used by the next patch, which intends to check
both the exit code and qemu-img's output.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 tests/qemu-iotests/iotests.py | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 5ea4c4df8b..eee94e18cc 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -29,7 +29,7 @@ import struct
 import subprocess
 import sys
 from typing import (Any, Callable, Dict, Iterable,
-                    List, Optional, Sequence, TypeVar)
+                    List, Optional, Sequence, Tuple, TypeVar)
 import unittest
 
 # pylint: disable=import-error, wrong-import-position
@@ -90,15 +90,23 @@ luks_default_secret_object = 'secret,id=keysec0,data=' + \
 luks_default_key_secret_opt = 'key-secret=keysec0'
 
 
-def qemu_img(*args):
-    '''Run qemu-img and return the exit code'''
-    devnull = open('/dev/null', 'r+')
-    exitcode = subprocess.call(qemu_img_args + list(args),
-                               stdin=devnull, stdout=devnull)
+def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
+    """
+    Run qemu-img and return both its output and its exit code
+    """
+    subp = subprocess.Popen(qemu_img_args + list(args),
+                            stdout=subprocess.PIPE,
+                            stderr=subprocess.STDOUT,
+                            universal_newlines=True)
+    exitcode = subp.wait()
     if exitcode < 0:
         sys.stderr.write('qemu-img received signal %i: %s\n'
                          % (-exitcode, ' '.join(qemu_img_args + list(args))))
-    return exitcode
+    return (subp.communicate()[0], exitcode)
+
+def qemu_img(*args: str) -> int:
+    '''Run qemu-img and return the exit code'''
+    return qemu_img_pipe_and_status(*args)[1]
 
 def ordered_qmp(qmsg, conv_keys=True):
     # Dictionaries are not ordered prior to 3.6, therefore:
@@ -140,17 +148,9 @@ def qemu_img_verbose(*args):
                          % (-exitcode, ' '.join(qemu_img_args + list(args))))
     return exitcode
 
-def qemu_img_pipe(*args):
+def qemu_img_pipe(*args: str) -> str:
     '''Run qemu-img and return its output'''
-    subp = subprocess.Popen(qemu_img_args + list(args),
-                            stdout=subprocess.PIPE,
-                            stderr=subprocess.STDOUT,
-                            universal_newlines=True)
-    exitcode = subp.wait()
-    if exitcode < 0:
-        sys.stderr.write('qemu-img received signal %i: %s\n'
-                         % (-exitcode, ' '.join(qemu_img_args + list(args))))
-    return subp.communicate()[0]
+    return qemu_img_pipe_and_status(*args)[0]
 
 def qemu_img_log(*args):
     result = qemu_img_pipe(*args)
-- 
2.26.2