EndPointInternalError: The endpoint returned the HTTP status code 500.

Response:
b'{\n    "exception": "[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: \'<\'",\n    "query": "#\\nPREFIX biopax: <http://www.biopax.org/release/biopax-level3.owl#>\\nPREFIX bd: <http://www.bigdata.com/rdf#>\\nPREFIX cc: <http://creativecommons.org/ns#>\\nPREFIX datacite: <http://purl.org/spar/datacite/>\\nPREFIX dblp: <https://dblp.org/rdf/schema#>\\nPREFIX dc:    <http://purl.org/dc/elements/1.1/>\\nPREFIX dct: <http://purl.org/dc/terms/>\\nPREFIX freq:  <http://purl.org/cld/freq/>\\nPREFIX geo: <http://www.opengis.net/ont/geosparql#>\\nPREFIX geom: <http://geovocab.org/geometry#>\\nPREFIX gpml:  <http://vocabularies.wikipathways.org/gpml#>\\nPREFIX litre: <http://purl.org/spar/literal/> \\nPREFIX lgdo: <http://linkedgeodata.org/ontology/>\\nPREFIX ontolex: <http://www.w3.org/ns/lemon/ontolex#>\\nPREFIX orkgp: <http://orkg.org/orkg/predicate/>\\nPREFIX orkgc: <http://orkg.org/orkg/class/>\\nPREFIX orkgr: <http://orkg.org/orkg/resource/>\\nPREFIX owl: <http://www.w3.org/2002/07/owl#>\\nPREFIX p: <http://www.wikidata.org/prop/>\\nPREFIX pav: <http://purl.org/pav/>\\nPREFIX pq: <http://www.wikidata.org/prop/qualifier/>\\nPREFIX pqn: <http://www.wikidata.org/prop/qualifier/value-normalized/>\\nPREFIX pqv: <http://www.wikidata.org/prop/qualifier/value/>\\nPREFIX pr: <http://www.wikidata.org/prop/reference/>\\nPREFIX prn: <http://www.wikidata.org/prop/reference/value-normalized/>\\nPREFIX prov: <http://www.w3.org/ns/prov#>\\nPREFIX prv: <http://www.wikidata.org/prop/reference/value/>\\nPREFIX ps: <http://www.wikidata.org/prop/statement/>\\nPREFIX psn: <http://www.wikidata.org/prop/statement/value-normalized/>\\nPREFIX psv: <http://www.wikidata.org/prop/statement/value/>\\nPREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>\\nPREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\\nPREFIX schema: <http://schema.org/>\\nPREFIX skos: <http://www.w3.org/2004/02/skos/core#>\\nPREFIX void:  <http://rdfs.org/ns/void#>\\nPREFIX vrank: <http://purl.org/voc/vrank#>\\nPREFIX wd: <http://www.wikidata.org/entity/>\\nPREFIX wdata: <http://www.wikidata.org/wiki/Special:EntityData/>\\nPREFIX wdno: <http://www.wikidata.org/prop/novalue/>\\nPREFIX wdref: <http://www.wikidata.org/reference/>\\nPREFIX wds: <http://www.wikidata.org/entity/statement/>\\nPREFIX wdt: <http://www.wikidata.org/prop/direct/>\\nPREFIX wdtn: <http://www.wikidata.org/prop/direct-normalized/>\\nPREFIX wdv: <http://www.wikidata.org/value/>\\nPREFIX wikibase: <http://wikiba.se/ontology#>\\nPREFIX wp: <http://vocabularies.wikipathways.org/wp#>\\nPREFIX wprdf: <http://rdf.wikipathways.org/>\\nPREFIX xsd: <http://www.w3.org/2001/XMLSchema#>\\n\\nSELECT ?personLabel ?instanceLabel\\nWHERE\\n{\\n   SERVICE wikibase:label {\\n    bd:serviceParam wikibase:language \\"en\\" .\\n   }\\n  #?person wdt:P31/wdt:P279* wd:Q5.\\n  ?person wdt:P509 wd:Q3235597.\\n}",\n    "resultsize": 0,\n    "runtimeInformation": {\n        "cache_status": "computed",\n        "children": [\n            {\n                "cache_status": "computed",\n                "children": [],\n                "column_names": [\n                    "?person"\n                ],\n                "description": "IndexScan ?person <http://www.wikidata.org/prop/direct/P509> <http://www.wikidata.org/entity/Q3235597>",\n                "details": null,\n                "estimated_column_multiplicities": [\n                    1.0\n                ],\n                "estimated_operation_cost": 27,\n                "estimated_size": 27,\n                "estimated_total_cost": 27,\n                "operation_time": 0,\n                "original_operation_time": 0,\n                "original_total_time": 0,\n                "result_cols": 1,\n                "result_rows": 27,\n                "status": "fully materialized",\n                "total_time": 0\n            },\n            {\n                "cache_status": "computed",\n                "children": [],\n                "column_names": [],\n                "description": "Service with IRI <http://wikiba.se/ontology#label>",\n                "details": null,\n                "estimated_column_multiplicities": [],\n                "estimated_operation_cost": 1000000,\n                "estimated_size": 100000,\n                "estimated_total_cost": 1000000,\n                "operation_time": 111,\n                "original_operation_time": 0,\n                "original_total_time": 0,\n                "result_cols": 0,\n                "result_rows": 0,\n                "status": "failed",\n                "total_time": 111\n            }\n        ],\n        "column_names": [\n            "?person"\n        ],\n        "description": "Cartesian Product Join",\n        "details": null,\n        "estimated_column_multiplicities": [\n            1.0\n        ],\n        "estimated_operation_cost": 2700000,\n        "estimated_size": 2700000,\n        "estimated_total_cost": 3700027,\n        "operation_time": 0,\n        "original_operation_time": 0,\n        "original_total_time": 0,\n        "result_cols": 1,\n        "result_rows": 0,\n        "status": "failed because child failed",\n        "total_time": 111\n    },\n    "status": "ERROR",\n    "time": {\n        "computeResult": 113,\n        "total": 113\n    }\n}'