Use more robust path handling in test_syntax_error_includes_module to avoid flakiness when running via VS Code GUI

Author: nathanjmcdougall

tests/functional/test_error_handling.py

@@ -1,14 +1,15 @@
-import os
+from pathlib import Path
 
 import pytest  # type: ignore
 
 from grimp import build_graph, exceptions
 
 
 def test_syntax_error_includes_module():
-    dirname = os.path.dirname(__file__)
-    filename = os.path.abspath(
-        os.path.join(dirname, "..", "assets", "syntaxerrorpackage", "foo", "one.py")
+    filename = str(
+        (
+            Path(__file__).parent.parent / "assets" / "syntaxerrorpackage" / "foo" / "one.py"
+        ).resolve()
     )
 
     with pytest.raises(exceptions.SourceSyntaxError) as excinfo: