trig GRAPH needs graphname (as in w3c-test:trig-graph-bad-01)

[WhiteGobo]

Summary of changes

trig parser will now expect a graphname if Keyword GRAPH is used before {...}.
removed expected failure for testcase https://www.w3.org/2013/TrigTests/#trig-graph-bad-01

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• If the change has a potential impact on users of this project:
  • Added or updated tests that fail without the change.
  • Updated relevant documentation to avoid inaccuracies.
  • Considered adding additional documentation.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[coveralls]

coverage: 90.903% (+0.002%) from 90.901% when pulling c1bbb72 on WhiteGobo:trig-xfail-GRAPH-only-with-name into afea615 on RDFLib:main.

[aucampia]

Test file in question:

rdflib/test/data/suites/w3c/trig/trig-graph-bad-01.trig

Lines 1 to 5 in 6f53455

	# GRAPH tests
	PREFIX : <http://example/>
	# GRAPH but no name - GRAPH is not used with the default graph
	GRAPH { :s :p :o }

[aucampia]

Thanks for the fix, it looks good. I just made one suggestion regarding how the error is raised.

[aucampia]

I will merge later this week.