Plone 5.2 and Python 3 support

[buchi]

Adds support for Plone 5.2 and Python 3

Mainly compatibility fixes. Uses Plone's installer view PLIP 1340 if available and falls back to QuickInstaller if not.

[mauritsvanrees]

I tried it out, and seems to work on 5.2 Py 3. Note that I don't use the zcml upgrade steps, so I did not test those.

I have one problem though.
In the extras_require we have: 'colors': ['blessed <= 1.9.5']. That does not work on Python 3:

$ bin/upgrade plone_upgrade --all-sites
Traceback (most recent call last):
  File "/Users/maurits/.pyenv/versions/3.7.6/lib/python3.7/sre_parse.py", line 1015, in parse_template
    this = chr(ESCAPES[this][1])
KeyError: '\\d'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "bin/upgrade", line 308, in <module>
    import ftw.upgrade.command
  File "/Users/maurits/clients/zeelandia/plone52/develop/ftw.upgrade/ftw/upgrade/command/__init__.py", line 1, in <module>
    from ftw.upgrade.command import combine_bundles
  File "/Users/maurits/clients/zeelandia/plone52/develop/ftw.upgrade/ftw/upgrade/command/combine_bundles.py", line 5, in <module>
    from ftw.upgrade.command.terminal import TERMINAL
  File "/Users/maurits/clients/zeelandia/plone52/develop/ftw.upgrade/ftw/upgrade/command/terminal.py", line 30, in <module>
    TERMINAL = Terminal()
  File "/Users/maurits/shared-eggs/cp37m/blessed-1.9.5-py3.7.egg/blessed/terminal.py", line 207, in __init__
    for re_name, re_val in init_sequence_patterns(self).items():
  File "/Users/maurits/shared-eggs/cp37m/blessed-1.9.5-py3.7.egg/blessed/sequences.py", line 281, in init_sequence_patterns
    _wont_move = _merge_sequences(get_wontmove_sequence_patterns(term))
  File "/Users/maurits/shared-eggs/cp37m/blessed-1.9.5-py3.7.egg/blessed/sequences.py", line 233, in get_wontmove_sequence_patterns
    ] + list(map(re.escape, (term.r1, term.r2, term.r3,))))
  File "/Users/maurits/shared-eggs/cp37m/blessed-1.9.5-py3.7.egg/blessed/sequences.py", line 68, in _build_any_numeric_capability
    cap_re = re.sub('(\d+)', r'(\d+)', cap_re)
  File "/Users/maurits/.pyenv/versions/3.7.6/lib/python3.7/re.py", line 192, in sub
    return _compile(pattern, flags).sub(repl, string, count)
  File "/Users/maurits/.pyenv/versions/3.7.6/lib/python3.7/re.py", line 309, in _subx
    template = _compile_repl(template, pattern)
  File "/Users/maurits/.pyenv/versions/3.7.6/lib/python3.7/re.py", line 300, in _compile_repl
    return sre_parse.parse_template(repl, pattern)
  File "/Users/maurits/.pyenv/versions/3.7.6/lib/python3.7/sre_parse.py", line 1018, in parse_template
    raise s.error('bad escape %s' % this, len(this))
re.error: bad escape \d at position 1

The version restriction was added in 2015 to avoid a conflict with six pinning by Plone: 7f145e4
But blessings only requires six >= 1.9.0. This only conflicts with the 1.8.0 pin of Plone 4.3.8 and earlier, and 5.0.2 and earlier.
So I think it is fine to remove the version restriction on blessed from our setup.py. The latest blessed version seems to work on Python 2.7 too.

This could be done outside of this PR too, but it is most necessary for Python 3.

Workaround for users: do not add ftw.upgrade['colors'] to the eggs, but simply ftw.upgrade.
Then it seems to work fine with the python3 branch of this PR.
And actually, even with the colors extra I don't see any colors, except some green lines in the help text. There may be a few commands that are more colourful though.

[buchi]

@mauritsvanrees thanks for your feedback! I've removed the version constraint for blessed.

I've also cherry-picked your fix for the port number into this PR.

[deiferni]

Thanks for the mostly small and granular commits. Made reviewing this a bit easier.

Some comments/suggestions, but nothing that would block a merge. Some things i mentioned were fixed in later commits. Apart from that LGTM 👍.

Did a testrun upgrading https://github.com/4teamwork/opengever.core/ from 2019.1 to 2020.1. Worked flawlessly from what i can tell ✨.

[buchi]

@deiferni @mauritsvanrees thans for reviewing!