chore: use ConfigurationError when package_dir is outside cwd (#2898)

* chore: use ConfigurationError when package_dir is outside cwd

Replace a generic Exception with errors. ConfigurationError when package_dir is not inside the working directory. This makes the error type consistent with the project's error handling and allows the CLI to treat this as a fatal error with the expected exit behavior.

* test: merge linux package_dir test into linux_build_steps_test

Fold the standalone linux_build_test.py into the existing
linux_build_steps_test.py, which already covers the linux platform
build orchestration. Reuses the file's existing import boilerplate and
module-qualified build() call style.

Assisted-by: ClaudeCode:claude-opus-4.8
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Henry Schreiner <henryfs@princeton.edu>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

cibuildwheel/platforms/linux.py

@@ -493,7 +493,7 @@ def build(options: Options, tmp_path: Path) -> None:
     abs_package_dir = options.globals.package_dir.resolve()
     if cwd != abs_package_dir and cwd not in abs_package_dir.parents:
         msg = "package_dir must be inside the working directory"
-        raise Exception(msg)
+        raise errors.ConfigurationError(msg)
 
     container_project_path = PurePosixPath("/project")
     container_package_dir = container_project_path / abs_package_dir.relative_to(cwd)

unit_test/linux_build_steps_test.py

@@ -3,7 +3,10 @@ from __future__ import annotations
 import textwrap
 from pprint import pprint
 
+import pytest
+
 import cibuildwheel.platforms.linux
+from cibuildwheel.errors import ConfigurationError
 from cibuildwheel.oci_container import OCIContainerEngineConfig
 from cibuildwheel.options import CommandLineArguments, Options
 
@@ -11,8 +14,6 @@ TYPE_CHECKING = False
 if TYPE_CHECKING:
     from pathlib import Path
 
-    import pytest
-
 
 def test_linux_container_split(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     """
@@ -99,3 +100,24 @@ def test_linux_container_split(tmp_path: Path, monkeypatch: pytest.MonkeyPatch)
     ]
     assert before_alls(build_steps[3]) == [""] * 4
     assert container_engines(build_steps[3]) == [default_container_engine] * 4
+
+
+def test_package_dir_outside_working_directory_raises_configuration_error(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    work_dir = tmp_path / "work"
+    work_dir.mkdir()
+    package_dir = tmp_path / "package"
+    package_dir.mkdir()
+    package_dir.joinpath("pyproject.toml").touch()
+
+    monkeypatch.chdir(work_dir)
+
+    command_line_arguments = CommandLineArguments.defaults()
+    command_line_arguments.package_dir = package_dir
+    options = Options(platform="linux", command_line_arguments=command_line_arguments, env={})
+
+    with pytest.raises(
+        ConfigurationError, match="package_dir must be inside the working directory"
+    ):
+        cibuildwheel.platforms.linux.build(options, tmp_path / "build")