Merge ~mwhudson/curtin:fix-multipath-reuse into curtin:master

[Michael Hudson-Doyle]

block_meta: call realpath on partition node returned by sfdisk

sfdisk --json on a device mapper block device will "helpfully" return
paths like /device/mapper/mpatha-part1 for the "node" of each partition.
This doesn't work so well when you then assume that the basename of the
returned path is the kernel name for the device.

This fixes reusing a partition on a multipath disk.

This time for sure (tm)

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:c3ed71475cca693aa8f11fadbbab19bb7b88b630
https://jenkins.ubuntu.com/server/job/curtin-ci/256/
Executed test runs:
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-amd64/256/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-arm64/256/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-ppc64el/256/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-s390x/256/

Click here to trigger a rebuild:
https://jenkins.ubuntu.com/server/job/curtin-ci/256//rebuild

review: Approve (continuous-integration)

[Dan Bungert (dbungert)]

review: Approve

diff --git a/curtin/commands/block_meta.py b/curtin/commands/block_meta.py
index f3f19dc..fbbfeeb 100644
--- a/curtin/commands/block_meta.py
+++ b/curtin/commands/block_meta.py
@@ -820,7 +820,7 @@ def verify_ptable_flag(devpath, expected_flag, label, part_info):
 
 
 def partition_verify_sfdisk(part_action, label, sfdisk_part_info):
-    devpath = sfdisk_part_info['node']
+    devpath = os.path.realpath(sfdisk_part_info['node'])
     verify_size(
         devpath, int(util.human2bytes(part_action['size'])), sfdisk_part_info)
     expected_flag = part_action.get('flag')
diff --git a/tests/unittests/test_commands_block_meta.py b/tests/unittests/test_commands_block_meta.py
index 3e22792..7c8e7bf 100644
--- a/tests/unittests/test_commands_block_meta.py
+++ b/tests/unittests/test_commands_block_meta.py
@@ -2572,6 +2572,8 @@ class TestPartitionVerifySfdisk(CiTestCase):
         base = 'curtin.commands.block_meta.'
         self.add_patch(base + 'verify_size', 'm_verify_size')
         self.add_patch(base + 'verify_ptable_flag', 'm_verify_ptable_flag')
+        self.add_patch(base + 'os.path.realpath', 'm_realpath')
+        self.m_realpath.side_effect = lambda x: x
         self.info = {
             'id': 'disk-sda-part-2',
             'type': 'partition',