CorruptedSessionError: Value of key 'io_log_filename' cannot be None

While suspend tests got some troubles,

Trying to resume and got following error messages:

$ checkbox-cli
Do you want to resume the previous session? [y, n] y
CRITICAL plainbox.crashes: Executable 'checkbox' invoked with Namespace(check_config=False, command=<checkbox_ng.commands.cli.CliCommand object at 0x7f047c414208>, debug_console=False, debug_interrupt=False, dry_run=False, exclude_pattern_list=[], include_pattern_list=[], log_level=None, new_ui=False, not_interactive=False, pdb=False, providers=None, trace=[], whitelist=[]) has crashed
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/plainbox/impl/clitools.py", line 513, in dispatch_and_catch_exceptions
    return self.dispatch_command(ns)
  File "/usr/lib/python3/dist-packages/plainbox/impl/clitools.py", line 509, in dispatch_command
    return ns.command.invoked(ns)
  File "/usr/lib/python3/dist-packages/checkbox_ng/commands/cli.py", line 63, in invoked
    self.settings, ns).run()
  File "/usr/lib/python3/dist-packages/checkbox_ng/commands/oldcli.py", line 74, in run
    job_list, previous_session_file)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/manager.py", line 252, in load_session
    state = SessionResumeHelper(unit_list).resume(data, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 215, in resume
    return self._resume_json(json_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 237, in _resume_json
    self.job_list).resume_json(json_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 429, in resume_json
    return self._build_SessionState(session_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 455, in _build_SessionState
    self._restore_SessionState_jobs_and_results(session, session_repr)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 491, in _restore_SessionState_jobs_and_results
    self._process_job(session, jobs_repr, results_repr, job_id)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 562, in _process_job
    result = self._build_JobResult(result_repr)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 639, in _build_JobResult
    result_repr, key='io_log_filename', value_type=str)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 752, in _validate
    raise CorruptedSessionError(error_msg)
plainbox.impl.session.resume.CorruptedSessionError: Value of key 'io_log_filename' cannot be None
Traceback (most recent call last):
  File "/usr/bin/checkbox-cli", line 9, in <module>
    load_entry_point('checkbox-ng==0.4.dev', 'console_scripts', 'checkbox-cli')()
  File "/usr/lib/python3/dist-packages/checkbox_ng/main.py", line 175, in checkbox_cli
    CheckBoxNGTool().main(['checkbox-cli'] + args))
  File "/usr/lib/python3/dist-packages/plainbox/impl/clitools.py", line 291, in main
    return self.dispatch_and_catch_exceptions(ns)
  File "/usr/lib/python3/dist-packages/plainbox/impl/clitools.py", line 513, in dispatch_and_catch_exceptions
    return self.dispatch_command(ns)
  File "/usr/lib/python3/dist-packages/plainbox/impl/clitools.py", line 509, in dispatch_command
    return ns.command.invoked(ns)
  File "/usr/lib/python3/dist-packages/checkbox_ng/commands/cli.py", line 63, in invoked
    self.settings, ns).run()
  File "/usr/lib/python3/dist-packages/checkbox_ng/commands/oldcli.py", line 74, in run
    job_list, previous_session_file)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/manager.py", line 252, in load_session
    state = SessionResumeHelper(unit_list).resume(data, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 215, in resume
    return self._resume_json(json_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 237, in _resume_json
    self.job_list).resume_json(json_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 429, in resume_json
    return self._build_SessionState(session_repr, early_cb)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 455, in _build_SessionState
    self._restore_SessionState_jobs_and_results(session, session_repr)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 491, in _restore_SessionState_jobs_and_results
    self._process_job(session, jobs_repr, results_repr, job_id)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 562, in _process_job
    result = self._build_JobResult(result_repr)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 639, in _build_JobResult
    result_repr, key='io_log_filename', value_type=str)
  File "/usr/lib/python3/dist-packages/plainbox/impl/session/resume.py", line 752, in _validate
    raise CorruptedSessionError(error_msg)
plainbox.impl.session.resume.CorruptedSessionError: Value of key 'io_log_filename' cannot be None