[PATCH 16/22] tests/functional: add common deb_extract helper

["Daniel P. Berrangé" <berrange@redhat.com>]

This mirrors the existing archive_extract, cpio_extract and zip_extract
helpers

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tests/functional/qemu_test/linuxkernel.py | 15 +++++----------
 tests/functional/qemu_test/utils.py       | 13 +++++++++++++
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/tests/functional/qemu_test/linuxkernel.py b/tests/functional/qemu_test/linuxkernel.py
index a6525f9dd6..fb6a158d36 100644
--- a/tests/functional/qemu_test/linuxkernel.py
+++ b/tests/functional/qemu_test/linuxkernel.py
@@ -6,8 +6,8 @@
 import os
 
 from .testcase import QemuSystemTest
-from .cmd import run_cmd, wait_for_console_pattern
-from .utils import archive_extract
+from .cmd import wait_for_console_pattern
+from .utils import deb_extract
 
 class LinuxKernelTest(QemuSystemTest):
     KERNEL_COMMON_COMMAND_LINE = 'printk.time=0 '
@@ -37,16 +37,11 @@ def extract_from_deb(self, deb_path, path):
         :param path: path within the deb archive of the file to be extracted
         :returns: path of the extracted file
         """
-        cwd = os.getcwd()
-        os.chdir(self.workdir)
-        (stdout, stderr, ret) = run_cmd(['ar', 't', deb_path])
-        file_path = stdout.split()[2]
-        run_cmd(['ar', 'x', deb_path, file_path])
-        archive_extract(file_path, self.workdir)
-        os.chdir(cwd)
+        relpath = os.path.relpath(path, '/')
+        deb_extract(deb_path, self.workdir, member="." + path)
         # Return complete path to extracted file.  Because callers to
         # extract_from_deb() specify 'path' with a leading slash, it is
         # necessary to use 'relative_to()' to turn it into a relative
         # path for joining to the scratch dir
-        return os.path.normpath(self.scratch_file(os.path.relpath(path, '/')))
+        return os.path.normpath(self.scratch_file(relpath))
 
diff --git a/tests/functional/qemu_test/utils.py b/tests/functional/qemu_test/utils.py
index 41bd1df666..bafe7fb80e 100644
--- a/tests/functional/qemu_test/utils.py
+++ b/tests/functional/qemu_test/utils.py
@@ -15,6 +15,8 @@
 import subprocess
 import tarfile
 
+from .cmd import run_cmd
+
 """
 Round up to next power of 2
 """
@@ -53,6 +55,17 @@ def zip_extract(archive, dest_dir, member=None):
         else:
             zf.extractall(path=dest_dir)
 
+def deb_extract(archive, dest_dir, member=None):
+    cwd = os.getcwd()
+    os.chdir(dest_dir)
+    try:
+        (stdout, stderr, ret) = run_cmd(['ar', 't', archive])
+        file_path = stdout.split()[2]
+        run_cmd(['ar', 'x', archive, file_path])
+        archive_extract(file_path, dest_dir, member)
+    finally:
+        os.chdir(cwd)
+
 def gzip_uncompress(gz_path, output_path):
     if os.path.exists(output_path):
         return
-- 
2.46.0