title: Creating model_form raises 'SQLAlchemy' object has no attribute 'query' error
body: <p>I'm using WTForms' <code>model_form</code> to create a form based on a Flask-SQLAlchemy model.  If there is a foreign key on the model, I get <code>AttributeError: 'SQLAlchemy' object has no attribute 'query'</code>.  Why am I getting this error and how do I fix it?</p>
  
  <pre><code>from wtforms.ext.sqlalchemy.orm import model_form
  
  class BREADView(MethodView):        
      def __init__(self,endpoint_param,model_param,exclude=None):
          self.endpoint = endpoint_param;
          self.model = model_param;        
          self.path = url_for('.%s' % self.endpoint)
          self.DetailForm = model_form(self.model, db_session=db, base_class=Form )
          self.DetailForm.submit = SubmitField('Submit')   
  
      def get(self, obj_id='', operation=''):
          if operation == 'new':        
              new_form = self.DetailForm(request.form)            
              return render_template(
                  self.detail_template,
                  form=new_form,
              )
  </code></pre>
  
  
  
  <pre><code>Traceback (most recent call last):
    File "/bin/user_wsgi_wrapper.py", line 130, in __call__
      self.error_log_file.logger.exception("Error running WSGI application")
    File "/usr/lib/python3.4/logging/__init__.py", line 1296, in exception
      self.error(msg, *args, **kwargs)
    File "/usr/lib/python3.4/logging/__init__.py", line 1289, in error
      self._log(ERROR, msg, args, **kwargs)
    File "/usr/lib/python3.4/logging/__init__.py", line 1395, in _log
      self.handle(record)
    File "/usr/lib/python3.4/logging/__init__.py", line 1404, in handle
      if (not self.disabled) and self.filter(record):
    File "/usr/lib/python3.4/logging/__init__.py", line 692, in filter
      for f in self.filters:
    File "/bin/user_wsgi_wrapper.py", line 122, in __call__
      app_iterator = self.app(environ, start_response)
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1836, in __call__
      return self.wsgi_app(environ, start_response)
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1820, in wsgi_app
      response = self.make_response(self.handle_exception(e))
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1403, in handle_exception
      reraise(exc_type, exc_value, tb)
    File "/usr/local/lib/python3.4/dist-packages/flask/_compat.py", line 33, in reraise
      raise value
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1817, in wsgi_app
      response = self.full_dispatch_request()
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1477, in full_dispatch_request
      rv = self.handle_user_exception(e)
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1381, in handle_user_exception
      reraise(exc_type, exc_value, tb)
    File "/usr/local/lib/python3.4/dist-packages/flask/_compat.py", line 33, in reraise
      raise value
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1475, in full_dispatch_request
      rv = self.dispatch_request()
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1461, in dispatch_request
      return self.view_functions[rule.endpoint](**req.view_args)
    File "/usr/local/lib/python3.4/dist-packages/flask/views.py", line 84, in view
      return self.dispatch_request(*args, **kwargs)
    File "/usr/local/lib/python3.4/dist-packages/flask/views.py", line 149, in dispatch_request
      return meth(*args, **kwargs)
    File "/home/severedblue/mysite/app/uct/views.py", line 53, in get
      endpoint=self.endpoint,
    File "/usr/local/lib/python3.4/dist-packages/flask/templating.py", line 128, in render_template
      context, ctx.app)
    File "/usr/local/lib/python3.4/dist-packages/flask/templating.py", line 110, in _render
      rv = template.render(context)
    File "/usr/local/lib/python3.4/dist-packages/jinja2/environment.py", line 969, in render
      return self.environment.handle_exception(exc_info, True)
    File "/usr/local/lib/python3.4/dist-packages/jinja2/environment.py", line 742, in handle_exception
      reraise(exc_type, exc_value, tb)
    File "/usr/local/lib/python3.4/dist-packages/jinja2/_compat.py", line 36, in reraise
      raise value.with_traceback(tb)
    File "/home/severedblue/mysite/app/templates/form.html", line 2, in &lt;module&gt;
      {% import "bootstrap/wtf.html" as wtf %}
    File "/home/severedblue/mysite/app/templates/base.html", line 1, in &lt;module&gt;
      {% extends "bootstrap/base.html" %}
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 1, in &lt;module&gt;
      {% block doc -%}
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 4, in &lt;module&gt;
      {%- block html %}
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 20, in &lt;module&gt;
      {% block body -%}
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 23, in &lt;module&gt;
      {% block content -%}
    File "/home/severedblue/mysite/app/templates/base.html", line 23, in &lt;module&gt;
      {% block page_content %}{% endblock %}
    File "/home/severedblue/mysite/app/templates/form.html", line 11, in &lt;module&gt;
      {{ wtf.quick_form(form) }}
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 195, in &lt;module&gt;
      {{ form_field(field,
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 116, in &lt;module&gt;
      {{field(class="form-control", **kwargs)|safe}}
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/fields/core.py", line 149, in __call__
      return self.meta.render_field(self, kwargs)
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/meta.py", line 53, in render_field
      return field.widget(field, **render_kw)
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/widgets/core.py", line 280, in __call__
      for val, label, selected in field.iter_choices():
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/fields.py", line 107, in iter_choices
      for pk, obj in self._get_object_list():
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/fields.py", line 98, in _get_object_list
      query = self.query or self.query_factory()
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/orm.py", line 121, in &lt;lambda&gt;
      'query_factory': lambda: db_session.query(foreign_model).all()
  AttributeError: 'SQLAlchemy' object has no attribute 'query'
  </code></pre>