[leapp] system failed to boot at reboot stage, error "Command ['/bin/sed', '-i', 's/^DEFAULTKERNEL=kernel$/DEFAULTKERNEL=kernel-core/g', '/etc/sysconfig/kernel'] failed with exit code 2.' is seen

Issue

• Below traceback is observed during IPU reboot phase:

Nov 08 07:18:09 localhost upgrade[577]: ==> Processing phase `Preparation`
Nov 08 07:18:09 localhost upgrade[577]: ====> * remove_boot_files
Nov 08 07:18:09 localhost upgrade[577]:         Remove Leapp provided initramfs from boot partition.
Nov 08 07:18:09 localhost upgrade[577]: ====> * bind_update
Nov 08 07:18:09 localhost upgrade[577]:         Actor parsing facts found in configuration and modifying configuration.
Nov 08 07:18:09 localhost upgrade[577]: ====> * update_etc_sysconfig_kernel
Nov 08 07:18:09 localhost upgrade[577]:         Update /etc/sysconfig/kernel file.
Nov 08 07:18:09 localhost upgrade[1275]: Process Process-224:
Nov 08 07:18:09 localhost upgrade[1275]: Traceback (most recent call last):
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/lib64/python2.7/multiprocessing/process.py", line 258, in _bootstrap
Nov 08 07:18:09 localhost upgrade[1275]:     self.run()
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/lib64/python2.7/multiprocessing/process.py", line 114, in run
Nov 08 07:18:09 localhost upgrade[1275]:     self._target(*self._args, **self._kwargs)
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 74, in _do_run
Nov 08 07:18:09 localhost upgrade[1275]:     actor_instance.run(*args, **kwargs)
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/lib/python2.7/site-packages/leapp/actors/__init__.py", line 289, in run
Nov 08 07:18:09 localhost upgrade[1275]:     self.process(*args)
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/updateetcsysconfigkernel/actor.py", line 20, in process
Nov 08 07:18:09 localhost upgrade[1275]:     updateetcsysconfigkernel.update_kernel_config('/etc/sysconfig/kernel')
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/updateetcsysconfigkernel/libraries/updateetcsysconfigkernel.py", line 9, in update_kernel_config
Nov 08 07:18:09 localhost upgrade[1275]:     path])
Nov 08 07:18:09 localhost upgrade[1275]:   File "/usr/lib/python2.7/site-packages/leapp/libraries/stdlib/__init__.py", line 188, in run
Nov 08 07:18:09 localhost upgrade[1275]:     result=result
Nov 08 07:18:09 localhost upgrade[1275]: CalledProcessError: Command ['/bin/sed', '-i', 's/^DEFAULTKERNEL=kernel$/DEFAULTKERNEL=kernel-core/g', '/etc/sysconfig/kernel'] failed with exit code 2.
Nov 08 07:18:10 localhost upgrade[577]: ============================================================================================================
Nov 08 07:18:10 localhost upgrade[577]: Actor update_etc_sysconfig_kernel unexpectedly terminated with exit code: 1 - Please check the above details
Nov 08 07:18:10 localhost upgrade[577]: ============================================================================================================