fix: always parse HexTuple files as utf-8 (#2070)

Always parse HexTuple files as utf-8 as was the intent anyway as
evidenced by the code that will raise a warning if the encoding provided
for a HexTuple file is something other than utf-8 or None.

https://github.com/RDFLib/rdflib/blob/cfa418074b27b12aac905ba266b002a237c5ff4c/rdflib/plugins/parsers/hext.py#L73-L79

Not adding any tests as this code is already tested and an XFAIL is
removed in this patch.

CHANGELOG.md

@@ -215,6 +215,22 @@ and will be removed for release.
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+
+<!-- -->
+<!-- -->
+<!-- CHANGE BARRIER: START PR #2070 -->
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+
+- Always parse HexTuple files as utf-8. 
+  [PR #2070](https://github.com/RDFLib/rdflib/pull/2070).
+
+<!-- -->
+<!-- -->
+<!-- CHANGE BARRIER: END PR #2070 -->
+<!-- -->
+<!-- -->
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rdflib/plugins/parsers/hext.py

@@ -87,7 +87,7 @@ def parse(self, source, graph, **kwargs):
 
         # handle different source types - only file and string (data) for now
         if hasattr(source, "file"):
-            with open(source.file.name) as fp:
+            with open(source.file.name, encoding="utf-8") as fp:
                 for l in fp:
                     self._parse_hextuple(cg, self._load_json_line(l))
         elif hasattr(source, "_InputSource__bytefile"):

test/test_graph/test_variants.py

@@ -2,7 +2,6 @@
 import logging
 import os
 import re
-import sys
 from dataclasses import dataclass, field
 from pathlib import Path, PurePath
 from test.data import TEST_DATA_DIR
@@ -192,16 +191,6 @@ def for_directory(
     ),
 }
 
-if sys.platform == "win32":
-    EXPECTED_FAILURES["variants/diverse_triples"] = pytest.mark.xfail(
-        reason="""
-    Some encoding issue when parsing hext on windows:
-        >       return codecs.charmap_decode(input,self.errors,decoding_table)[0]
-        E       UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 356: character maps to <undefined>
-        """,
-        raises=UnicodeDecodeError,
-    )
-
 
 def tests_found() -> None:
     logging.debug("VARIANTS_DIR = %s", VARIANTS_DIR)