fix: drop Cirrus CI (going away June 1, 2026) (#2817)

* fix: drop Cirrus CI (going away June 1, 2026)

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* Restore missing note

* Update CI services documentation for Cirrus CI

Removed official support for Cirrus CI due to end-of-life.

---------

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

cibuildwheel/ci.py

@@ -14,7 +14,6 @@ class CIProvider(Enum):
     azure_pipelines = "azure_pipelines"
     github_actions = "github_actions"
     gitlab = "gitlab"
-    cirrus_ci = "cirrus_ci"
 
     # unofficial support
     appveyor = "appveyor"
@@ -35,8 +34,6 @@ def detect_ci_provider() -> CIProvider | None:
         return CIProvider.github_actions
     elif "GITLAB_CI" in os.environ:
         return CIProvider.gitlab
-    elif "CIRRUS_CI" in os.environ:
-        return CIProvider.cirrus_ci
     elif strtobool(os.environ.get("CI", "false")):
         return CIProvider.other
     else:

cibuildwheel/platforms/linux.py

@@ -481,8 +481,7 @@ def build(options: Options, tmp_path: Path) -> None:
                 Docker or Podman is required to run Linux builds. If you're
                 building on Travis CI, add `services: [docker]` to your
                 .travis.yml. If you're building on Circle CI in Linux, add a
-                `setup_remote_docker` step to your .circleci/config.yml. If
-                you're building on Cirrus CI, use `docker_builder` task.
+                `setup_remote_docker` step to your .circleci/config.yml.
                 """
             )
             raise errors.ConfigurationError(msg) from error