https://github.com/schollii/pypubsub/issues/63

Python 3.14 environments commonly carry newer setuptools.  The upstream
setuptools <77 cap is not tied to a known incompatibility and blocks builds
with current Python packaging stacks.

The contrib namespace contains stale Python 2 example code that setuptools
installs as importable modules when namespace discovery is enabled.

--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=68,<77", "wheel", "setuptools-scm>=7"]
+requires = ["setuptools>=68", "wheel", "setuptools-scm>=7"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -61,4 +61,5 @@
 pubsub = ["LICENSE_BSD_Simple.txt", "RELEASE_NOTES.txt", "py.typed"]
 
 [tool.setuptools.packages.find]
 where = ["src"]
+exclude = ["contrib*"]