KeyError with NumberRange validator

[stlehmann]

This issue occurs when validators have been added to a Flask-Admin field via the form_args attribute. It appeares when using the NumberRange validator but others might be concerned as well. A false validation of the NumberRange validator will result in a KeyError. This is due to the message string getting passed to gettext with formatting keys but without values.

2017-01-16 21:16:10,570] ERROR in app: Exception on /fabric/edit/ [POST]
Traceback (most recent call last):
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/app.py", line 1517, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/_compat.py", line 33, in reraise
    raise value
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/app.py", line 1612, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask/app.py", line 1598, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/base.py", line 69, in inner
    return self._run_view(f, *args, **kwargs)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/base.py", line 368, in _run_view
    return fn(self, *args, **kwargs)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/model/base.py", line 1973, in edit_view
    if self.validate_form(form):
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/model/base.py", line 1290, in validate_form
    return validate_form_on_submit(form)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/helpers.py", line 65, in validate_form_on_submit
    return is_form_submitted() and form.validate()
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/form.py", line 310, in validate
    return super(Form, self).validate(extra)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/form.py", line 152, in validate
    if not field.validate(self, extra):
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/fields/core.py", line 204, in validate
    stop_validation = self._run_validation_chain(form, chain)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/fields/core.py", line 224, in _run_validation_chain
    validator(form, self)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/validators.py", line 139, in __call__
    message = field.gettext('Number must be at least %(min)s.')
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/wtforms/fields/core.py", line 164, in gettext
    return self._translations.gettext(string)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_admin/babel.py", line 55, in gettext
    return wtforms_domain.gettext(string)
  File "/Users/stefan/Documents/python/projects/inventory/venv/lib/python3.6/site-packages/flask_babelex/__init__.py", line 534, in gettext
    return t.ugettext(string) % variables
KeyError: 'min'