fix pytest>=7.0.0 error

- fixes computationalmodelling#180

nbval/plugin.py

@@ -16,6 +16,7 @@
 import warnings
 from collections import OrderedDict, defaultdict
 
+from pathlib import Path
 from queue import Empty
 
 # for reading notebook files
@@ -141,7 +142,10 @@ def pytest_collect_file(path, parent):
     if (opt.nbval or opt.nbval_lax) and path.fnmatch("*.ipynb"):
         # https://docs.pytest.org/en/stable/deprecations.html#node-construction-changed-to-node-from-parent
         if hasattr(IPyNbFile, "from_parent"):
-            return IPyNbFile.from_parent(parent, fspath=path)
+            try:
+                return IPyNbFile.from_parent(parent, path=Path(path))
+            except Exception:  # Pytest < 7.0
+                return IPyNbFile.from_parent(parent, fspath=path)
         else:  # Pytest < 5.4
             return IPyNbFile(path, parent)