validators.NumberRange doesn't handle NaN

[jon-brenner]

Validating a DecimalField with a NumberRange validator throws a decimal.InvalidOperation exception when the value of the field is NaN. I would expect validation to fail instead

File "/usr/local/lib/python3.6/dist-packages/wtforms/form.py", line 310, in validate
  return super(Form, self).validate(extra)
File "/usr/local/lib/python3.6/dist-packages/wtforms/form.py", line 152, in validate
  if not field.validate(self, extra):
File "/usr/local/lib/python3.6/dist-packages/wtforms/fields/core.py", line 206, in validate
  stop_validation = self._run_validation_chain(form, chain)
File "/usr/local/lib/python3.6/dist-packages/wtforms/fields/core.py", line 226, in _run_validation_chain
  validator(form, self)
File "/usr/local/lib/python3.6/dist-packages/wtforms/validators.py", line 134, in __call__
  if data is None or (self.min is not None and data < self.min) or 
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]

[azmeuk]

I could reproduce this with both master and 2.2-maintenance.

>>> import wtforms
>>> from tests.common import DummyPostData
>>> class F(wtforms.Form):
...      a = wtforms.DecimalField(validators=[wtforms.validators.NumberRange(min=0, max=1)])
>>> F(DummyPostData({"a": "NaN"})).validate()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/azmeuk/dev/wtforms/wtforms/form.py", line 310, in validate
    return super(Form, self).validate(extra)
  File "/home/azmeuk/dev/wtforms/wtforms/form.py", line 152, in validate
    if not field.validate(self, extra):
  File "/home/azmeuk/dev/wtforms/wtforms/fields/core.py", line 206, in validate
    stop_validation = self._run_validation_chain(form, chain)
  File "/home/azmeuk/dev/wtforms/wtforms/fields/core.py", line 226, in _run_validation_chain
    validator(form, self)  
  File "/home/azmeuk/dev/wtforms/wtforms/validators.py", line 134, in __call__   
    if data is None or (self.min is not None and data < self.min) or 
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]
[<class 'decimal.InvalidOperation'>]