Move localloop to exec_sudo

One call in localloop requires the output of the command, so modify
exec_sudo to buffer up output and return it.  This is modelled on the
same thing in package-installs-v2 which seems to work.  Rather than
return a subprocess exception, return a dib exception which everything
should have imported anyway.

The overall reason for this is to make our external calls more
consistent for mocking in unit testing.

Change-Id: I10d23b873dee9f775daef2a4c8be5671d02c386e

diskimage_builder/block_device/level0/localloop.py

@@ -14,12 +14,12 @@
 
 import logging
 import os
-import subprocess
 
 from diskimage_builder.block_device.exception import \
     BlockDeviceSetupException
 from diskimage_builder.block_device.plugin import NodeBase
 from diskimage_builder.block_device.plugin import PluginBase
+from diskimage_builder.block_device.utils import exec_sudo
 from diskimage_builder.block_device.utils import parse_abs_size_spec
 
 
@@ -41,17 +41,11 @@ def image_delete(filename):
 def loopdev_attach(filename):
     logger.info("loopdev attach")
     logger.debug("Calling [sudo losetup --show -f %s]", filename)
-    subp = subprocess.Popen(["sudo", "losetup", "--show", "-f",
-                             filename], stdout=subprocess.PIPE)
-    rval = subp.wait()
-    if rval == 0:
-        # [:-1]: Cut of the newline
-        block_device = subp.stdout.read()[:-1].decode("utf-8")
-        logger.info("New block device [%s]", block_device)
-        return block_device
-    else:
-        logger.error("losetup failed")
-        raise BlockDeviceSetupException("losetup failed")
+    block_device = exec_sudo(["losetup", "--show", "-f", filename])
+    # [:-1]: Cut of the newline
+    block_device = block_device[:-1]
+    logger.info("New block device [%s]", block_device)
+    return block_device
 
 
 def loopdev_detach(loopdev):
@@ -59,19 +53,16 @@ def loopdev_detach(loopdev):
     # loopback dev may be tied up a bit by udev events triggered
     # by partition events
     for try_cnt in range(10, 1, -1):
-        logger.debug("Calling [sudo losetup -d %s]", loopdev)
-        subp = subprocess.Popen(["sudo", "losetup", "-d",
-                                 loopdev])
-        rval = subp.wait()
-        if rval == 0:
-            logger.info("Successfully detached [%s]", loopdev)
-            return 0
-        else:
-            logger.error("loopdev detach failed")
+        try:
+            exec_sudo(["losetup", "-d", loopdev])
+            return
+        except BlockDeviceSetupException as e:
             # Do not raise an error - maybe other cleanup methods
             # can at least do some more work.
+            logger.error("loopdev detach failed (%s)", e.returncode)
+
     logger.debug("Gave up trying to detach [%s]", loopdev)
-    return rval
+    return 1
 
 
 class LocalLoopNode(NodeBase):

diskimage_builder/block_device/level1/lvm.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 import logging
-import subprocess
 
 from diskimage_builder.block_device.exception \
     import BlockDeviceSetupException
@@ -313,8 +312,8 @@ class LVMUmountNode(NodeBase):
     def umount(self):
         try:
             exec_sudo(['pvscan', '--cache'])
-        except subprocess.CalledProcessError as cpe:
-            logger.debug("pvscan call result [%s]", cpe)
+        except BlockDeviceSetupException as e:
+            logger.info("pvscan call failed [%s]", e.returncode)
 
     def get_edges(self):
         # This node depends on all physical device(s), which is

diskimage_builder/block_device/utils.py

@@ -12,10 +12,14 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import locale
 import logging
 import re
 import subprocess
 
+from diskimage_builder.block_device.exception import \
+    BlockDeviceSetupException
+
 logger = logging.getLogger(__name__)
 
 
@@ -95,10 +99,16 @@ def exec_sudo(cmd):
     at debug levels.
 
     Arguments:
-    :param cmd: str command list; for Popen()
-    :return: nothing
-    :raises: subprocess.CalledProcessError if return code != 0
 
+    :param cmd: str command list; for Popen()
+    :return: the stdout+stderror of the called command
+    :raises BlockDeviceSetupException: if return code != 0.
+
+    Exception values similar to ``subprocess.CalledProcessError``
+
+    * ``returncode`` : returncode of child
+    * ``cmd`` : the command run
+    * ``output`` : stdout+stderr output
     """
     assert isinstance(cmd, list)
     sudo_cmd = ["sudo"]
@@ -116,10 +126,20 @@ def exec_sudo(cmd):
                             stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
 
-    for line in iter(proc.stdout.readline, b""):
-        logger.debug("exec_sudo: %s", line.rstrip())
-
+    out = ""
+    with proc.stdout:
+        for line in iter(proc.stdout.readline, b''):
+            line = line.decode(encoding=locale.getpreferredencoding(False),
+                               errors='backslashreplace')
+            out += line
+            logger.debug("exec_sudo: %s", line.rstrip())
     proc.wait()
-    if proc.returncode != 0:
-        raise subprocess.CalledProcessError(proc.returncode,
-                                            ' '.join(sudo_cmd))
+
+    if proc.returncode:
+        e = BlockDeviceSetupException("exec_sudo failed")
+        e.returncode = proc.returncode
+        e.cmd = ' '.join(sudo_cmd)
+        e.output = out
+        raise e
+
+    return out