TypeError: <pydruid.utils.filters.Filter instance at 0x7f38cc1bbb48> is not JSON serializable

[x4base]

It seems that this line in #387 causes a new bug
File "/projects/druid/panoramix/caravel/models.py", line 1116, in query
query_str += json.dumps(qry, indent=2)

because qry['filter'] is a Filter instance

Stack:
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1381, in handle_user_exception
Open an interactive python shell in this framereraise(exc_type, exc_value, tb)
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/lib/python2.7/site-packages/Flask-0.10.1-py2.7.egg/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/usr/lib/python2.7/site-packages/Flask_AppBuilder-1.6.0-py2.7.egg/flask_appbuilder/security/decorators.py", line 26, in wraps
return f(self, *args, **kwargs)
File "/usr/lib/python2.7/site-packages/caravel-0.8.8-py2.7.egg/caravel/models.py", line 1176, in wrapper
return f(*args, **kwargs)
File "/usr/lib/python2.7/site-packages/caravel-0.8.8-py2.7.egg/caravel/views.py", line 514, in explore
raise e

Traceback (most recent call last):
  File "/projects/druid/panoramix/caravel/views.py", line 510, in explore
    payload = obj.get_json()
  File "/projects/druid/panoramix/caravel/viz.py", line 251, in get_json
    'data': self.get_data(),
  File "/projects/druid/panoramix/caravel/viz.py", line 745, in get_data
    df = self.get_df()
  File "/projects/druid/panoramix/caravel/viz.py", line 140, in get_df
    self.results = self.datasource.query(**query_obj)
  File "/projects/druid/panoramix/caravel/models.py", line 1116, in query
    query_str += json.dumps(qry, indent=2)
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/__init__.py", line 250, in dumps
    sort_keys=sort_keys, **kw).encode(obj)
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/encoder.py", line 209, in encode
    chunks = list(chunks)
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/encoder.py", line 434, in _iterencode
    for chunk in _iterencode_dict(o, _current_indent_level):
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/encoder.py", line 408, in _iterencode_dict
    for chunk in chunks:
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/encoder.py", line 442, in _iterencode
    o = _default(o)
  File "/Users/clu/.pyenv/versions/2.7.5/lib/python2.7/json/encoder.py", line 184, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: <pydruid.utils.filters.Filter instance at 0x10ae1d128> is not JSON serializable

[mistercrunch]

#391