Add test to confirm allow_infos and allow_warnings validate() API

This test demonstrates the current implementation state fails.
A follow-on patch will correct the issue.

References:
* #126
* The general style of this test was adapted from
  `/test/issues/test_96.py`.

Signed-off-by: Alex Nelson <alexander.nelson@nist.gov>

test/issues/test_126.py

@@ -0,0 +1,114 @@
+# -*- coding: utf-8 -*-
+#
+
+# This software was developed at the National Institute of Standards
+# and Technology by employees of the Federal Government in the course
+# of their official duties. Pursuant to title 17 Section 105 of the
+# United States Code this software is not subject to copyright
+# protection and is in the public domain. NIST assumes no
+# responsibility whatsoever for its use by other parties, and makes
+# no guarantees, expressed or implied, about its quality,
+# reliability, or any other characteristic.
+#
+# We would appreciate acknowledgement if the software is used.
+
+"""
+https://github.com/RDFLib/pySHACL/issues/126
+"""
+
+from typing import Optional
+
+from pyshacl import validate
+from rdflib import Namespace, SH, URIRef
+
+NS_EX = Namespace("http://example.org/ns#")
+
+mixed_file_text = """
+@prefix ex: <http://example.org/ns#> .
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix sh: <http://www.w3.org/ns/shacl#> .
+@prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .
+
+ex:myProperty-datatype
+	a sh:PropertyShape ;
+	rdfs:comment "Violations of sh:datatype are produced as warnings"@en ;
+	sh:datatype xsd:string ;
+	sh:path ex:myProperty ;
+	sh:severity sh:Warning ;
+	.
+
+ex:myProperty-maxLength
+	a sh:PropertyShape ;
+	rdfs:comment "The default severity here is sh:Info"@en ;
+	sh:maxLength 10 ;
+	sh:message "Too many characters"@en ;
+	sh:path ex:myProperty ;
+	sh:severity sh:Info ;
+	.
+
+ex:MyShape
+	a sh:NodeShape ;
+	rdfs:comment "This example was adapted from the example shapes and validation graph in the Severity section of the SHACL specification."@en ;
+	rdfs:seeAlso "https://www.w3.org/TR/shacl/#severity" ;
+	sh:property
+		ex:myProperty-datatype ,
+		ex:myProperty-maxLength
+		;
+	sh:targetNode ex:MyInstance ;
+	.
+
+ex:MyInstance
+	rdfs:comment "This instance triggers one Info-level and one Warning-level violation."@en ;
+	ex:myProperty "http://toomanycharacters"^^xsd:anyURI ;
+	.
+"""
+
+
+def _test_126_template(expected_conformance: bool, allow_level: Optional[URIRef] = None) -> None:
+    validate_kwargs: Dict[Any] = {"data_graph_format": "turtle", "shacl_graph_format": "turtle", "debug": True}
+    if allow_level is None:
+        pass
+    elif allow_level == SH.Info:
+        validate_kwargs["allow_infos"] = True
+    elif allow_level == SH.Warning:
+        validate_kwargs["allow_warnings"] = True
+    else:
+        raise NotImplementedError("allow_level=%r" % allow_level)
+
+    res1 = validate(mixed_file_text, **validate_kwargs)
+    conforms, graph, string = res1
+    assert conforms == expected_conformance
+
+    datatype_shape_reported = False
+    maxlength_shape_reported = False
+
+    # Confirm the report graph emits ValidationResults pertaining to each expected triggering property shape.
+    for triple in graph.triples((None, SH.sourceShape, NS_EX["myProperty-datatype"])):
+        datatype_shape_reported = True
+    for triple in graph.triples((None, SH.sourceShape, NS_EX["myProperty-maxLength"])):
+        maxlength_shape_reported = True
+
+    assert datatype_shape_reported
+    assert maxlength_shape_reported
+
+
+def test_126_1() -> None:
+    """
+    With no severities allowed, expect non-conformance.
+    """
+    _test_126_template(False)
+
+
+def test_126_2() -> None:
+    """
+    With Infos allowed, expect non-conformance.
+    """
+    _test_126_template(False, SH.Info)
+
+
+def test_126_3() -> None:
+    """
+    With Warnings allowed, expect conformance.
+    """
+    _test_126_template(True, SH.Warning)