IN-923 Raise exceptions for failed connection tests

Why these changes are being introduced:
* Raising exceptions for any failed connection tests stops the application
from proceeding with the workflow once a connection test fails.
This logic makes sense as the (1) a successful connection to the Data Warehouse
is required for any Carbon run and (2) a successful connection
to the Elements FTP server is required for any run Carbon run that involves FTP.

How this addresses that need:
* Exceptions are raised in the connection test functions of
carbon.database.DatabaseEngine and
carbon.app.DatabaseToFtpPipe.
* CLI tests for failed connection tests are properly configured.

Side effects of this change:
* None

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/IN-923

carbon/app.py

@@ -244,6 +244,7 @@ def run_connection_test(self) -> None:
                 f"Failed to connect to the Symplectic Elements FTP server: {error}"
             )
             logger.exception(error_message)
+            raise
         else:
             logger.info("Successfully connected to the Symplectic Elements FTP server")
             ftps.quit()

carbon/database.py

@@ -114,6 +114,7 @@ def run_connection_test(self) -> None:
         except Exception as error:
             error_message = f"Failed to connect to the Data Warehouse: {error}"
             logger.exception(error_message)
+            raise
         else:
             dbapi_connection = connection.connection
             version = (

tests/test_cli.py

@@ -188,11 +188,19 @@ def test_cli_connection_tests_success(caplog, functional_engine, runner):
     assert "Successfully connected to the Symplectic Elements FTP server" in caplog.text
 
 
-def test_cli_connection_tests_fail(
-    caplog, ftp_server, monkeypatch, nonfunctional_engine, runner
+def test_cli_database_connection_test_fails(caplog, nonfunctional_engine, runner):
+    with patch("carbon.cli.DatabaseEngine") as mocked_engine:
+        mocked_engine.return_value = nonfunctional_engine
+        result = runner.invoke(main, ["--run_connection_tests"])
+        assert result.exit_code == 1
+
+    assert "Failed to connect to the Data Warehouse" in caplog.text
+
+
+def test_cli_ftp_connection_test_fails(
+    caplog, ftp_server, functional_engine, monkeypatch, runner
 ):
     ftp_socket, _ = ftp_server
-
     monkeypatch.setenv(
         "SYMPLECTIC_FTP_JSON",
         (
@@ -202,10 +210,10 @@ def test_cli_connection_tests_fail(
             '"SYMPLECTIC_FTP_PASS": "invalid_password"}'
         ),
     )
+
     with patch("carbon.cli.DatabaseEngine") as mocked_engine:
-        mocked_engine.return_value = nonfunctional_engine
+        mocked_engine.return_value = functional_engine
         result = runner.invoke(main, ["--run_connection_tests"])
-        assert result.exit_code == 0
+        assert result.exit_code == 1
 
-    assert "Failed to connect to the Data Warehouse" in caplog.text
     assert "Failed to connect to the Symplectic Elements FTP server" in caplog.text