Fix flake8 errors and update changelog

docs/main/changelog.rst

@@ -7,6 +7,12 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+Development version
+-------------------
+- Fix wiring to not crash on missing signatures.
+  See issue: `#420 <https://github.com/ets-labs/python-dependency-injector/issues/420>`_.
+  Thanks to `@Balthus1989 <https://github.com/Balthus1989>`_ for reporting the issue.
+
 4.29.1
 ------
 - Fix recursive copying issue in ``Delegate`` provider.

src/dependency_injector/wiring.py

@@ -481,7 +481,7 @@ def _unpatch_attribute(patched: PatchedAttribute) -> None:
     setattr(patched.member, patched.name, patched.marker)
 
 
-def _fetch_reference_injections(
+def _fetch_reference_injections(  # noqa: C901
         fn: Callable[..., Any],
 ) -> Tuple[Dict[str, Any], Dict[str, Any]]:
     # Hotfix, see: