Added a dummy DummyExecFactory.

In case of using an external DB for the RunDbTest command, the task SpawnTestEnvironment does not return a valid `container_info` for the Database (which makes totally sense because the external db can be a None-Docker Exasol DB). However, also the using `SshExecFactory` does not work because the user/pwd are not returned from SpawnTestEnvironment.
=> Added a DummyExecFactory which implements the interface but does nothing and throws an exception in case the `exec` function gets invoked.

exasol_script_languages_container_tool/lib/api/run_db_tests.py

@@ -5,6 +5,8 @@
 from exasol_integration_test_docker_environment.lib.api.common import run_task, generate_root_task, \
     set_docker_repository_config, set_build_config, import_build_steps, cli_function
 from exasol_integration_test_docker_environment.lib.base.dependency_logger_base_task import DependencyLoggerBaseTask
+from exasol_integration_test_docker_environment.lib.test_environment.parameter.docker_db_test_environment_parameter import \
+    DbOsAccess
 
 from exasol_script_languages_container_tool.lib.api import api_errors
 from exasol_script_languages_container_tool.lib.tasks.test.test_container import TestContainer, AllTestsResult
@@ -126,6 +128,7 @@ def root_task_generator() -> DependencyLoggerBaseTask:
                                   reuse_database_setup=reuse_database_setup,
                                   reuse_test_container=reuse_test_container,
                                   reuse_database=reuse_database,
+                                  db_os_access=DbOsAccess[db_os_access],
                                   no_test_container_cleanup_after_success=reuse_test_container,
                                   no_test_container_cleanup_after_failure=reuse_test_container,
                                   no_database_cleanup_after_success=reuse_database,

exasol_script_languages_container_tool/lib/tasks/test/test_runner_db_test_task.py

@@ -2,8 +2,9 @@
 from typing import Generator, Any, Dict
 
 import luigi
+from docker.models.containers import ExecResult
 from exasol_integration_test_docker_environment.lib.base.db_os_executor import DbOsExecFactory, SshExecFactory, \
-    DockerClientFactory, DockerExecFactory
+    DockerClientFactory, DockerExecFactory, DbOsExecutor
 from exasol_integration_test_docker_environment.lib.base.json_pickle_parameter import JsonPickleParameter
 from exasol_integration_test_docker_environment.lib.data.database_info import DatabaseInfo
 from exasol_integration_test_docker_environment.lib.test_environment.parameter.docker_db_test_environment_parameter import \
@@ -26,6 +27,26 @@
 from exasol_integration_test_docker_environment.lib.test_environment.spawn_test_environment import SpawnTestEnvironment
 
 
+class DummyExecutor(DbOsExecutor):
+
+    def exec(self, cmd: str) -> ExecResult:
+        raise RuntimeError("Not supposed to be called.")
+
+    def prepare(self):
+        pass
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type_, value, traceback):
+        pass
+
+
+class DummyExecFactory(DbOsExecFactory):
+    def executor(self) -> DbOsExecutor:
+        return DummyExecutor()
+
+
 class TestRunnerDBTestTask(FlavorBaseTask,
                            SpawnTestEnvironmentParameter,
                            RunDBTestsInTestConfigParameter):
@@ -71,10 +92,13 @@ def run_task(self):
         self.return_object(test_results)
 
     def _executor_factory(self, database_info: DatabaseInfo) -> DbOsExecFactory:
+
         if self.db_os_access == DbOsAccess.SSH:
             return SshExecFactory.from_database_info(database_info)
         client_factory = DockerClientFactory(timeout=100000)
-        return DockerExecFactory(database_info.container_info.container_name, client_factory)
+        if database_info.container_info is not None:
+            return DockerExecFactory(database_info.container_info.container_name, client_factory)
+        return DummyExecFactory()
 
     def upload_container(self, database_credentials: DatabaseCredentials, export_info: ExportInfo):
         reuse = \