working on cibw config

pyproject.toml

@@ -11,6 +11,7 @@ classifiers = [
     "Operating System :: OS Independent",
 ]
 keywords = ['symmetry', 'molecules', 'chemistry']
+requires-python = ">=3.9"
 
 [project.urls]
 Homepage = "https://github.com/corinwagen/pymsym"
@@ -24,3 +25,7 @@ extra_deps = [
 [build-system]
 requires = ["scikit-build-core"]
 build-backend = "scikit_build_core.build"
+
+[tool.cibuildwheel]
+# Disable building PyPy wheels on all platforms
+skip = "pp*"