pytest-localserver is still actively used in tests/conftest.py (imported as pytest_localserver.http.WSGIServer), which CapturingServer extends and which is consumed by test_transport.py and test_gevent.py — removing it from requirements will cause import errors and test failures.

Removing pytest-localserver from requirements-testing.txt will cause an ImportError at test collection time because tests/conftest.py unconditionally imports from pytest_localserver.http import WSGIServer, crashing the entire test suite.