Add a Tree widget (when label is None and value ends with '.json' or '.xml' and when value is a dict)

[fgallaire]

No description provided.

[PierreRaybaut]

With Python 3.4.4 64bits on Windows:

Traceback (most recent call last):
  File "C:\Python\formlayout\examples\tree.py", line 37, in <module>
    print('result:', fedit(datalist, title='Tree examples', type='questions'))
  File "C:\Python\formlayout\formlayout.py", line 1285, in fedit
    apply, ok, cancel, result, outfile, type, scrollbar)
  File "C:\Python\formlayout\formlayout.py", line 1093, in __init__
    self.formwidget.setup()
  File "C:\Python\formlayout\formlayout.py", line 640, in setup
    object_pairs_hook=OrderedDict)
  File "C:\WinPython-64bit-3.4.4.3\python-3.4.4.amd64\lib\json\__init__.py", line 268, in load
    parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
  File "C:\WinPython-64bit-3.4.4.3\python-3.4.4.amd64\lib\json\__init__.py", line 331, in loads
    return cls(**kw).decode(s)
  File "C:\WinPython-64bit-3.4.4.3\python-3.4.4.amd64\lib\json\decoder.py", line 343, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "C:\WinPython-64bit-3.4.4.3\python-3.4.4.amd64\lib\json\decoder.py", line 361, in raw_decode
    raise ValueError(errmsg("Expecting value", s, err.value)) from None
ValueError: Expecting value: line 1 column 1 (char 0)

[fgallaire]

I can't test my fix, so tell me if it's good.
"The default encoding is platform dependent (whatever locale.getpreferredencoding() returns)"

[PierreRaybaut]

There is still the same traceback with Python 3.5:

Traceback (most recent call last):
  File "C:\Python\formlayout\examples\tree.py", line 37, in <module>
    print('result:', fedit(datalist, title='Tree examples', type='questions'))
  File "C:\Python\formlayout\formlayout.py", line 1289, in fedit
    apply, ok, cancel, result, outfile, type, scrollbar)
  File "C:\Python\formlayout\formlayout.py", line 1097, in __init__
    self.formwidget.setup()
  File "C:\Python\formlayout\formlayout.py", line 644, in setup
    object_pairs_hook=OrderedDict)
  File "C:\WinPython-64bit-3.5.2.1Qt5\python-3.5.2.amd64\lib\json\__init__.py", line 268, in load
    parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
  File "C:\WinPython-64bit-3.5.2.1Qt5\python-3.5.2.amd64\lib\json\__init__.py", line 332, in loads
    return cls(**kw).decode(s)
  File "C:\WinPython-64bit-3.5.2.1Qt5\python-3.5.2.amd64\lib\json\decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "C:\WinPython-64bit-3.5.2.1Qt5\python-3.5.2.amd64\lib\json\decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

[lesteve]

We could set-up AppVeyor to test on Windows. I'll try to look at it next week at one point.

[fgallaire]

New fix, tests welcome!