Internal server error

[Baguage]

Traceback (most recent call last):

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/django/core/handlers/base.py", line 113, in get_response
response = callback(request, _callback_args, *_callback_kwargs)

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/django/views/generic/base.py", line 68, in view
return self.dispatch(request, _args, *_kwargs)

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/django/views/generic/base.py", line 86, in dispatch
return handler(request, _args, *_kwargs)

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/django/views/generic/base.py", line 153, in get
context = self.get_context_data(**kwargs)

File "/opt/portal/dw.vecnet.org/datawarehouse/views/CubeResultsView.py", line 271, in get_context_data
agg_result = browser.aggregate(new_cell, drilldown=[a]) # and aggregate the data

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/cubes/backends/sql/star.py", line 331, in aggregate
drilldown=drilldown)

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/cubes/backends/sql/star.py", line 567, in aggregation_statement
if attr in attributes]

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/cubes/backends/sql/star.py", line 1042, in column
table = self.table(ref.schema, ref.table)

File "/opt/venv/dw.vecnet.org/lib/python2.7/site-packages/cubes/backends/sql/star.py", line 1018, in table
(aliased_ref, self.cube.name) )

ModelError: Table with reference (None, u'subgroup') not found. Missing join in cube 'households'?

<WSGIRequest
path:/datawarehouse/results/,
GET:<QueryDict: {u'cube': [u'households'], u'num_measures': [u'1'], u'drillpath': [u'admin0|year||'], u'num_slices': [u'0'], u'interface': [u'native'], u'drilldim': [u'location|date_cubes|source|subgroup']}>,
POST:<QueryDict: {}>,
COOKIES:{'csrftoken': ''},
META:{'CONTEXT_DOCUMENT_ROOT': '/opt/portal/dw.vecnet.org/',
'CONTEXT_PREFIX': '',
u'CSRF_COOKIE': u'',
'DOCUMENT_ROOT': '/opt/portal/dw.vecnet.org/',
'GATEWAY_INTERFACE': 'CGI/1.1',
'HTTP_ACCEPT': 'application/json, text/javascript, /; q=0.01',
'HTTP_ACCEPT_ENCODING': 'gzip, deflate',
'HTTP_ACCEPT_LANGUAGE': 'en-AU',
'HTTP_CACHE_CONTROL': 'max-age=0',
'HTTP_CONNECTION': 'keep-alive',
'HTTP_COOKIE': 'csrftoken=',
'HTTP_HOST': 'dw.vecnet.org',
'HTTP_REFERER': 'https://dw.vecnet.org/datawarehouse/cube',
'HTTP_SURROGATE_CAPABILITY': 'contentkeeper-cache="Surrogate/1.0"',
'HTTP_USER_AGENT': 'Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko',
'HTTP_X_REQUESTED_WITH': 'XMLHttpRequest',
'PATH_INFO': u'/datawarehouse/results/',
'PATH_TRANSLATED': '/opt/portal/dw.vecnet.org/VECNet/wsgi.py/datawarehouse/results/',
'QUERY_STRING': 'num_slices=0&cube=households&num_measures=1&drilldim=location%7Cdate_cubes%7Csource%7Csubgroup&drillpath=admin0%7Cyear%7C%7C&interface=native',
'REMOTE_ADDR': '152.91.8.168',
'REMOTE_PORT': '19040',
'REQUEST_METHOD': 'GET',
'REQUEST_SCHEME': 'https',
'REQUEST_URI': '/datawarehouse/results/?num_slices=0&cube=households&num_measures=1&drilldim=location%7Cdate_cubes%7Csource%7Csubgroup&drillpath=admin0%7Cyear%7C%7C&interface=native',
'SCRIPT_FILENAME': '/opt/portal/dw.vecnet.org/VECNet/wsgi.py',
'SCRIPT_NAME': u'',
'SERVER_ADDR': '129.74.246.151',
'SERVER_ADMIN': 'avyushko@nd.edu',
'SERVER_NAME': 'dw.vecnet.org',
'SERVER_PORT': '443',
'SERVER_PROTOCOL': 'HTTP/1.1',
'SERVER_SIGNATURE': '',
'SERVER_SOFTWARE': 'Apache/2.4.6 (Red Hat Enterprise Linux) OpenSSL/1.0.1e-fips mod_wsgi/3.4 Python/2.7.5',
'SSL_TLS_SNI': 'dw.vecnet.org',
'UNIQUE_ID': 'V05z9fKsnILP@y35onGMoQAAAAw',
'mod_wsgi.application_group': 'dw.vecnet.org|',
'mod_wsgi.callable_object': 'application',
'mod_wsgi.enable_sendfile': '0',
'mod_wsgi.handler_script': '',
'mod_wsgi.input_chunked': '0',
'mod_wsgi.listener_host': '',
'mod_wsgi.listener_port': '443',
'mod_wsgi.process_group': 'wellbeing',
'mod_wsgi.queue_start': '1464759285150637',
'mod_wsgi.request_handler': 'wsgi-script',
'mod_wsgi.script_reloading': '1',
'mod_wsgi.version': (3, 4),
'wsgi.errors': <mod_wsgi.Log object at 0x7fb21e4e7570>,
'wsgi.file_wrapper': <built-in method file_wrapper of mod_wsgi.Adapter object at 0x7fb208060030>,
'wsgi.input': <mod_wsgi.Input object at 0x7fb20804c030>,
'wsgi.multiprocess': True,
'wsgi.multithread': True,
'wsgi.run_once': False,
'wsgi.url_scheme': 'https',
'wsgi.version': (1, 0)}>