Change pytest deprecation warnings into errors for 6.0 release (#7362)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

testing/example_scripts/fixtures/custom_item/conftest.py

@@ -1,10 +1,15 @@
 import pytest
 
 
-class CustomItem(pytest.Item, pytest.File):
+class CustomItem(pytest.Item):
     def runtest(self):
         pass
 
 
+class CustomFile(pytest.File):
+    def collect(self):
+        yield CustomItem.from_parent(name="foo", parent=self)
+
+
 def pytest_collect_file(path, parent):
-    return CustomItem(path, parent)
+    return CustomFile.from_parent(fspath=path, parent=parent)

testing/example_scripts/issue88_initial_file_multinodes/conftest.py

@@ -3,11 +3,11 @@ import pytest
 
 class MyFile(pytest.File):
     def collect(self):
-        return [MyItem("hello", parent=self)]
+        return [MyItem.from_parent(name="hello", parent=self)]
 
 
 def pytest_collect_file(path, parent):
-    return MyFile(path, parent)
+    return MyFile.from_parent(fspath=path, parent=parent)
 
 
 class MyItem(pytest.Item):