Fix indexing issues

[vemonet]

python3 etl/index_shapes.py gitlab shacl-shapes

Found 3 relevant SPARQL endpoints, but encoding error

Returns:

INFO:[04/19/2021, 09:55:12] SPARQL endpoint failed: http://digital-agenda-data.eu/data/sparqlbyte indices must be integers or slices, not str
INFO:[04/19/2021, 09:55:21] SPARQL endpoint failed: http://el.dbpedia.org/sparqlEndPointInternalError: endpoint returned code 500 and response. Response:b'Virtuoso 42000 Error The estimated execution time 2928956 (sec) exceeds the limit of 900 (sec).\n\nSPARQL query:\nSELECT * WHERE { ?s ?p ?o } LIMIT 10'
INFO:[04/19/2021, 09:55:25] SPARQL endpoint failed: http://cr.eionet.europa.eu/sparqlbyte indices must be integers or slices, not str