[ruff] Activate use next(iter(x)) instead of list(x)[0] and fix issue

Author: Pierre-Sassoulas

pyproject.toml

@@ -160,7 +160,6 @@ ignore = [
     # ruff ignore
     "RUF005", # Consider `(x, *y)` instead of concatenation
     "RUF012", # Mutable class attributes should be annotated with `typing.ClassVar`
-    "RUF015", # Prefer `next(iter(x))` over single element slice
 ]
 
 [tool.ruff.format]

testing/python/collect.py

@@ -1209,7 +1209,7 @@ def test_bar(self):
         classcol = pytester.collect_by_name(modcol, "TestClass")
         assert isinstance(classcol, Class)
         path, lineno, msg = classcol.reportinfo()
-        func = list(classcol.collect())[0]
+        func = next(iter(classcol.collect()))
         assert isinstance(func, Function)
         path, lineno, msg = func.reportinfo()