refactor: extract signal_alert into its own module

Move signal_alert out of python/common.py into a dedicated
python/signal_alert.py module and update its importers
(validate_system.py, snapshot_manager.py) to the new path.

Relocate the signal_alert tests from tests/test_common.py into
tests/test_signal_alert.py, repatching python.signal_alert.logger and
python.signal_alert.Apprise to match the new module.

tests/test_common.py

@@ -2,15 +2,7 @@
 
 from __future__ import annotations
 
-from os import environ
-from typing import TYPE_CHECKING
-
-from apprise import Apprise
-
-from python.common import bash_wrapper, signal_alert, utcnow
-
-if TYPE_CHECKING:
-    from pytest_mock import MockerFixture
+from python.common import bash_wrapper, utcnow
 
 
 def test_utcnow() -> None:
@@ -18,34 +10,6 @@ def test_utcnow() -> None:
     utcnow()
 
 
-def test_signal_alert(mocker: MockerFixture) -> None:
-    """test_signal_alert."""
-    environ["SIGNAL_ALERT_FROM_PHONE"] = "1234567890"
-    environ["SIGNAL_ALERT_TO_PHONE"] = "0987654321"
-
-    mock_logger = mocker.patch("python.common.logger")
-    mock_apprise_client = mocker.MagicMock(spec=Apprise)
-    mocker.patch("python.common.Apprise", return_value=mock_apprise_client)
-
-    signal_alert("test")
-
-    mock_logger.info.assert_not_called()
-    mock_apprise_client.add.assert_called_once_with("signal://localhost:8989/1234567890/0987654321")
-    mock_apprise_client.notify.assert_called_once_with(title="", body="test")
-
-
-def test_signal_alert_no_phones(mocker: MockerFixture) -> None:
-    """test_signal_alert_no_phones."""
-    if "SIGNAL_ALERT_FROM_PHONE" in environ:
-        del environ["SIGNAL_ALERT_FROM_PHONE"]
-    if "SIGNAL_ALERT_TO_PHONE" in environ:
-        del environ["SIGNAL_ALERT_TO_PHONE"]
-    mock_logger = mocker.patch("python.common.logger")
-    signal_alert("test")
-
-    mock_logger.info.assert_called_once_with("SIGNAL_ALERT_FROM_PHONE or SIGNAL_ALERT_TO_PHONE not set")
-
-
 def test_test_bash_wrapper() -> None:
     """test_test_bash_wrapper."""
     stdout, returncode = bash_wrapper("echo test")

tests/test_signal_alert.py

@@ -0,0 +1,41 @@
+"""test_signal_alert."""
+
+from __future__ import annotations
+
+from os import environ
+from typing import TYPE_CHECKING
+
+from apprise import Apprise
+
+from python.signal_alert import signal_alert
+
+if TYPE_CHECKING:
+    from pytest_mock import MockerFixture
+
+
+def test_signal_alert(mocker: MockerFixture) -> None:
+    """test_signal_alert."""
+    environ["SIGNAL_ALERT_FROM_PHONE"] = "1234567890"
+    environ["SIGNAL_ALERT_TO_PHONE"] = "0987654321"
+
+    mock_logger = mocker.patch("python.signal_alert.logger")
+    mock_apprise_client = mocker.MagicMock(spec=Apprise)
+    mocker.patch("python.signal_alert.Apprise", return_value=mock_apprise_client)
+
+    signal_alert("test")
+
+    mock_logger.info.assert_not_called()
+    mock_apprise_client.add.assert_called_once_with("signal://localhost:8989/1234567890/0987654321")
+    mock_apprise_client.notify.assert_called_once_with(title="", body="test")
+
+
+def test_signal_alert_no_phones(mocker: MockerFixture) -> None:
+    """test_signal_alert_no_phones."""
+    if "SIGNAL_ALERT_FROM_PHONE" in environ:
+        del environ["SIGNAL_ALERT_FROM_PHONE"]
+    if "SIGNAL_ALERT_TO_PHONE" in environ:
+        del environ["SIGNAL_ALERT_TO_PHONE"]
+    mock_logger = mocker.patch("python.signal_alert.logger")
+    signal_alert("test")
+
+    mock_logger.info.assert_called_once_with("SIGNAL_ALERT_FROM_PHONE or SIGNAL_ALERT_TO_PHONE not set")