[OE-core] [PATCH] wic: make engine.py:get_partitions() resilient to parted/dmidecode stderr output

[Geoff Parker]

Running wic commands on Debian 10 systems fail in
scripts/lib/wic/engine.py:get_partitions() due to new stderr output captured
when trying to parse the output from /sbin/parted as a non-root user.

The parted command calls the dmidecode utility, which produces this error
as a non-root user:
  /sys/firmware/dmi/tables/smbios_entry_point: Permission denied
  /dev/mem: Permission denied

scripts/lib/wic/engine.py:get_partitions()
calls misc.py:exec_cmd(), a subprocess wrapper which returns a
combined stderr and sdtdout.
These messages to stderr confuse the partition table parser in get_partitions().

This patch has the partition table parser ignore lines before the
expected "BYT;"
header string.

Running wic in Debian 9 does not have this issue.
---
 scripts/lib/wic/engine.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/scripts/lib/wic/engine.py b/scripts/lib/wic/engine.py
index f0c5ff0aaf..52c9592b33 100644
--- a/scripts/lib/wic/engine.py
+++ b/scripts/lib/wic/engine.py
@@ -266,10 +266,15 @@ class Disk:
             out = exec_cmd("%s -sm %s unit B print" % (self.parted,
self.imagepath))
             parttype = namedtuple("Part", "pnum start end size fstype")
             splitted = out.splitlines()
-            lsector_size, psector_size, self._ptable_format =
splitted[1].split(":")[3:6]
+            # skip over possible errors in exec_cmd output
+            try:
+                idx =splitted.index("BYT;")
+            except ValueError:
+                raise WicError("Error getting partition information
from %s" % (self.parted))
+            lsector_size, psector_size, self._ptable_format =
splitted[idx + 1].split(":")[3:6]
             self._lsector_size = int(lsector_size)
             self._psector_size = int(psector_size)
-            for line in splitted[2:]:
+            for line in splitted[idx + 2:]:
                 pnum, start, end, size, fstype = line.split(':')[:5]
                 partition = parttype(int(pnum), int(start[:-1]), int(end[:-1]),
                                      int(size[:-1]), fstype)
-- 
2.19.1