Generate empty report correctly

[pirat89]

On Python2, the json.dumps library can produce either unicode or str output. Nowadays, the unicode is required, however in case the input for json.dumps function does not contain any unicode objects (e.g. when no report entry exists), it produces str type.

Also ensure the generated json file has the empty newline in the end of the file.

Relates: #821 JIRA: OAMG-8996

Additional info:

(Pdb) json.dumps({'entries': [], 'leapp_run_id': context}, indent=2, ensure_ascii=False)
'{\n  "leapp_run_id": "c6aa7f2a-7aaf-4fc0-9bd3-667f81395e9f", \n  "entries": []\n}'
(Pdb) json.dumps({'entries': ["foo"], 'leapp_run_id': context}, indent=2, ensure_ascii=False)
'{\n  "leapp_run_id": "c6aa7f2a-7aaf-4fc0-9bd3-667f81395e9f", \n  "entries": [\n    "foo"\n  ]\n}'
(Pdb) json.dumps({'entries': [u"foo"], 'leapp_run_id': context}, indent=2, ensure_ascii=False)
u'{\n  "leapp_run_id": "c6aa7f2a-7aaf-4fc0-9bd3-667f81395e9f", \n  "entries": [\n    "foo"\n  ]\n}'
(Pdb) 

Original issue when an empty report has been generated:

Traceback (most recent call last):
  File "/usr/bin/leapp", line 9, in <module>
    load_entry_point('leapp==0.15.1', 'console_scripts', 'leapp')()
  File "/usr/lib/python2.7/site-packages/leapp/cli/__init__.py", line 45, in main
    cli.command.execute('leapp version {}'.format(VERSION))
  File "/usr/lib/python2.7/site-packages/leapp/utils/clicmd.py", line 111, in execute
    args.func(args)
  File "/usr/lib/python2.7/site-packages/leapp/utils/clicmd.py", line 133, in called
    self.target(args)
  File "/usr/lib/python2.7/site-packages/leapp/cli/commands/upgrade/breadcrumbs.py", line 163, in wrapper
    return f(*args, breadcrumbs=breadcrumbs, **kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/cli/commands/preupgrade/__init__.py", line 78, in preupgrade
    util.generate_report_files(context, report_schema)
  File "/usr/lib/python2.7/site-packages/leapp/cli/commands/upgrade/util.py", line 147, in generate_report_files
    generate_report_file(messages, context, report_json, report_schema)
  File "/usr/lib/python2.7/site-packages/leapp/utils/report.py", line 168, in generate_report_file
    f.write(data)
TypeError: must be unicode, not str

[github-actions[bot]]

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[fernflower]

/rerun

[github-actions[bot]]

Copr build succeeded: https://copr.fedorainfracloud.org/coprs/build/5890445

[pirat89]

@fernflower aah. copy&paste error /o\ should be fixed now

[pirat89]

/rerun

[github-actions[bot]]

Copr build succeeded: https://copr.fedorainfracloud.org/coprs/build/5890572

[github-actions[bot]]

Testing Farm request for RHEL-7.9-rhui/5886104;5890445 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-8.6-rhui/5886104;5890572 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-7.9-rhui/5886104;5890572 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[fernflower]

/rerun

[github-actions[bot]]

Copr build succeeded: https://copr.fedorainfracloud.org/coprs/build/5900120

[github-actions[bot]]

Testing Farm request for RHEL-8.6-rhui/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-7.9-rhui/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-8.6.0-Nightly/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-8.8.0-Nightly/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-7.9-ZStream/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.

[github-actions[bot]]

Testing Farm request for RHEL-7.9-ZStream/5886104;5900120 regression testing has been created. Once finished, results should be available here. Full pipeline log.