Be more descriminating on Accept headers sent based on different queries. Queries build using the DSL use either RDF content types, or SPARQL Results content types, not both.

Those using RDF content types:

 * CONSTRUCT, DESCRIBE, DELETE DATA, LOAD, CREATE

Those using SPARQL Results content types:

  * ASK, SELECT, INSERT DATA, CLEAR, DROP

Hopefully, this makes issues such as come up in #51 less likely to happen.
Update code setting appropriate Accept header, and also add */*;q=0.1 to every request as a fallback.
Only use DELETE DATA for #delete_statements if the statement is both constant, and contains no BNodes, otherwise, it falls back to DELETE/INSERT.
Check error response outputs query.
When doing updates, change BNodes to Variables.
Add around block with response delegation to capture query and report on queries run in this example if the example fails. (Not perfect, but still useful).
Remove debug point.
Be more descriminating on Accept headers sent based on different queries. Queries build using the DSL use either RDF content types, or SPARQL Results content types, not both. This includes adding */*;q=0.1 to all requests.

Those using RDF content types:

 * CONSTRUCT, DESCRIBE, DELETE DATA, LOAD, CREATE

Those using SPARQL Results content types:

  * ASK, SELECT, INSERT DATA, CLEAR, DROP

Hopefully, this makes issues such as come up in #51 less likely to happen.

Only use DELETE DATA for #delete_statements if the statement is both constant, and contains no BNodes, otherwise, it falls back to DELETE/INSERT.

Check error response includes query in exception.
When doing updates, change BNodes to Variables.