test: set locale for test_install_packages_error

tests/helper.py

@@ -4,6 +4,7 @@
 import functools
 import importlib.machinery
 import importlib.util
+import locale
 import os
 import pathlib
 import shutil
@@ -103,6 +104,14 @@ def read_shebang(command: str) -> str | None:
     return first_line.decode().split(" ", 1)[0][2:]
 
 
+@contextlib.contextmanager
+def restore_locale(category: int) -> Generator[None]:
+    """Restore locale after leaving this context manager."""
+    orig_locale = locale.getlocale(category)
+    yield
+    locale.setlocale(category, orig_locale)
+
+
 @contextlib.contextmanager
 def restore_os_environ() -> Generator[None]:
     """Restore os.environ after leaving this context manager."""

tests/system/test_packaging_apt_dpkg.py

@@ -4,6 +4,7 @@
 
 import glob
 import gzip
+import locale
 import os
 import pathlib
 import shutil
@@ -17,7 +18,7 @@
 import pytest
 
 from apport.packaging_impl.apt_dpkg import _parse_deb822_sources, impl
-from tests.helper import has_internet
+from tests.helper import has_internet, restore_locale
 from tests.paths import get_test_data_directory
 
 if shutil.which("dpkg") is None:
@@ -348,10 +349,12 @@ def test_install_packages_system(
 
 
 @pytest.mark.skipif(not has_internet(), reason="online test")
+@restore_locale(locale.LC_MESSAGES)
 def test_install_packages_error(
     configdir: str, cachedir: str, rootdir: str, apt_style: AptStyle
 ) -> None:
     """install_packages() with errors"""
+    locale.setlocale(locale.LC_MESSAGES, "C.UTF-8")
     # sources.list with invalid format
     release = _setup_foonux_config(configdir, apt_style)
     with open(