[tests] linkcheck: bind each test HTTP server to a unique port per-testcase (sphinx-doc#12126)

Co-authored-by: Bénédikt Tran <[email protected]>

Author: jayaddison

CHANGES.rst

@@ -155,6 +155,10 @@ Testing
 
 * pytest: report the result of ``test_run_epubcheck`` as ``skipped`` instead of
   ``success`` when Java and/or the ``epubcheck.jar`` code are not available.
+* utils: use dynamic allocation of unused port numbers for the test HTTP(S)
+  servers.  As a side-effect, this removes the need for test server lockfiles,
+  meaning that any remaining ``tests/test-server.lock`` files can safely be
+  deleted.
 
 Release 7.2.6 (released Sep 13, 2023)
 =====================================

pyproject.toml

@@ -94,7 +94,6 @@ test = [
     "defusedxml>=0.7.1", # for secure XML/HTML parsing
     "cython>=3.0",
     "setuptools>=67.0",  # for Cython compilation
-    "filelock",
 ]
 
 [[project.authors]]