Parser error

[hsolbrig]

"<S1> {<p1> [<o1>]} produces the following trace:

    ...
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser/ShExDocParser.py", line 1011, in accept
    return visitor.visitShapeExprDecl(self)
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser_impl/shex_doc_parser.py", line 67, in visitShapeExprDecl
    label = self.context.shapeexprlabel_to_IRI(ctx.shapeExprLabel())
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser_impl/parser_context.py", line 129, in shapeexprlabel_to_IRI
    return self.iri_to_iriref(shapeExprLabel.iri())
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser_impl/parser_context.py", line 115, in iri_to_iriref
    return ShExJ.IRIREF(self.iri_to_str(iri_))
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser_impl/parser_context.py", line 107, in iri_to_str
    return self.iriref_to_str(iri_.IRIREF())
  File "/Users/mrf7578/Development/git/shexSpec/grammar/parsers/python/pyshexc/parser_impl/parser_context.py", line 68, in iriref_to_str
    return rval if ':' in rval else self.base.val + rval
AttributeError: 'NoneType' object has no attribute 'val'

[hsolbrig]

The shexTest.validation suite expects the base to derive from the file name. We also need to add the ability to pass a default_base into the parser itself