PG question failed to render

Unable to obtain error messages from within the PG question.

WeBWorK Warnings

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Warning messages

debug is turned on in IO.pm. at [PG]/lib/WeBWorK/PG/IO.pm line 228
IO::query_sage_server(): SAGE CALL: /usr/bin/curl -i -k -sS -L --data-urlencode "accepted_tos=true" --data-urlencode 'user_expressions={"WEBWORK":"_webwork_safe_json(WEBWORK)"}' --data-urlencode "code=set_random_seed(323)
WEBWORK={}
def _webwork_safe_json(o):
import json
def default(o):
try:
if isinstance(o,sage.rings.integer.Integer):
json_obj = int(o)
elif isinstance(o,(sage.rings.real_mpfr.RealLiteral, sage.rings.real_mpfr.RealNumber)):
json_obj = float(o)
elif sage.modules.free_module_element.is_FreeModuleElement(o):
json_obj = list(o)
elif sage.matrix.matrix.is_Matrix(o):
json_obj = [list(i) for i in o.rows()]
elif isinstance(o, SageObject):
json_obj = repr(o)
else:
raise TypeError
except TypeError:
pass
else:
return json_obj
# Let the base class default method raise the TypeError
return json.JSONEncoder.default(self, o)
return json.dumps(o, default=default)
A= random_matrix(QQ,4,5,algorithm='echelonizable',rank=3).rows()
print A" https://sagecell.sagemath.org/service
RETURN from sage call
HTTP/1.1 100 (Continue)
HTTP/1.1 200 OK
Content-Length: 305
Server: TornadoServer/4.1
Access-Control-Allow-Credentials: true
Date: Wed, 27 May 2015 19:49:30 GMT
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=UTF-8
{"execute_reply": {"status": "ok", "execution_count": 1, "payload": [], "user_expressions": {"WEBWORK": {"status": "ok", "data": {"text/plain": "'{}'"}, "metadata": {}}}, "user_variables": {}}, "success": true, "stdout": "[(0, -3, 9, 1, 0), (1, -1, 8, -2, 3), (-1, -1, -2, 3, -3), (-3, 3, -24, 8, -9)]\n"}
END SAGE CALL at [PG]/lib/WeBWorK/PG/IO.pm line 231
IO::askSage: We have some kind of value |{"execute_reply": {"status": "ok", "execution_count": 1, "payload": [], "user_expressions": {"WEBWORK": {"status": "ok", "data": {"text/plain": "'{}'"}, "metadata": {}}}, "user_variables": {}}, "success": true, "stdout": "[(0, -3, 9, 1, 0), (1, -1, 8, -2, 3), (-1, -1, -2, 3, -3), (-3, 3, -24, 8, -9)]\n"}| returned from sage at [PG]/lib/WeBWorK/PG/IO.pm line 306
decoded contents
type = HASH; {
execute_reply => type = HASH; {
execution_count => 1
payload => type = ARRAY; ( )
status => ok
user_expressions => type = HASH; {
WEBWORK => type = HASH; {
data => type = HASH; {
text/plain => '{}'
}
metadata => type = HASH; {
}
status => ok
}
}
user_variables => type = HASH; {
}
}
stdout => [(0, -3, 9, 1, 0), (1, -1, 8, -2, 3), (-1, -1, -2, 3, -3), (-3, 3, -24, 8, -9)]
success => type = JSON::XS::Boolean; true
}
end decoded contents at [PG]/lib/WeBWorK/PG/IO.pm line 315
success is true at [PG]/lib/WeBWorK/PG/IO.pm line 321
sage_WEBWORK_data '{}' at [PG]/lib/WeBWorK/PG/IO.pm line 327
no content in WEBWORK variable. Returning stdout[(0, -3, 9, 1, 0), (1, -1, 8, -2, 3), (-1, -1, -2, 3, -3), (-3, 3, -24, 8, -9)]
Processing of this PG problem was not completed. Probably because of a syntax error.
The translator died prematurely and no PG warning messages were transmitted. at /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/Problem.pm line 932.