**Apache Airflow version: 2.0.1**
**What happened:**
Running an airflow dags test or backfill  CLI command shown in tutorial, produces the same error.

**dags test cli command result：**

```
(airflow_venv) (base) app@lunar_01:airflow$ airflow dags test tutorial 2015-06-01
[2021-02-16 04:29:22,355] {dagbag.py:448} INFO - Filling up the DagBag from /home/app/Lunar/src/airflow/dags
[2021-02-16 04:29:22,372] {example_kubernetes_executor_config.py:174} WARNING - Could not import DAGs in example_kubernetes_executor_config.py: No module named 'kubernetes'
[2021-02-16 04:29:22,373] {example_kubernetes_executor_config.py:175} WARNING - Install kubernetes dependencies with: pip install apache-airflow['cncf.kubernetes']
Traceback (most recent call last):
  File "/home/app/airflow_venv/bin/airflow", line 10, in <module>
    sys.exit(main())
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/cli/cli_parser.py", line 48, in command
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/cli.py", line 89, in wrapper
    return f(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/cli/commands/dag_command.py", line 389, in dag_test
    dag.run(executor=DebugExecutor(), start_date=args.execution_date, end_date=args.execution_date)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/models/dag.py", line 1706, in run
    job.run()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/base_job.py", line 237, in run
    self._execute()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 805, in _execute
    session=session,
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 715, in _execute_for_run_dates
    tis_map = self._task_instances_for_dag_run(dag_run, session=session)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 359, in _task_instances_for_dag_run
    dag_run.refresh_from_db()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/models/dagrun.py", line 178, in refresh_from_db
    DR.run_id == self.run_id,
  File "/home/app/airflow_venv/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 3500, in one
    raise orm_exc.NoResultFound("No row was found for one()")
sqlalchemy.orm.exc.NoResultFound: No row was found for one()
```

**backfill cli command result:**
```
(airflow_venv) (base) app@lunar_01:airflow$ airflow dags backfill tutorial --start-date 2015-06-01 --end-date 2015-06-07
/home/app/airflow_venv/lib/python3.7/site-packages/airflow/cli/commands/dag_command.py:62 PendingDeprecationWarning: --ignore-first-depends-on-past is deprecated as the value is always set to True
[2021-02-16 04:30:16,979] {dagbag.py:448} INFO - Filling up the DagBag from /home/app/Lunar/src/airflow/dags
[2021-02-16 04:30:16,996] {example_kubernetes_executor_config.py:174} WARNING - Could not import DAGs in example_kubernetes_executor_config.py: No module named 'kubernetes'
[2021-02-16 04:30:16,996] {example_kubernetes_executor_config.py:175} WARNING - Install kubernetes dependencies with: pip install apache-airflow['cncf.kubernetes']
Traceback (most recent call last):
  File "/home/app/airflow_venv/bin/airflow", line 10, in <module>
    sys.exit(main())
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/cli/cli_parser.py", line 48, in command
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/cli.py", line 89, in wrapper
    return f(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/cli/commands/dag_command.py", line 116, in dag_backfill
    run_backwards=args.run_backwards,
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/models/dag.py", line 1706, in run
    job.run()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/base_job.py", line 237, in run
    self._execute()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 805, in _execute
    session=session,
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 715, in _execute_for_run_dates
    tis_map = self._task_instances_for_dag_run(dag_run, session=session)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/jobs/backfill_job.py", line 359, in _task_instances_for_dag_run
    dag_run.refresh_from_db()
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/app/airflow_venv/lib/python3.7/site-packages/airflow/models/dagrun.py", line 178, in refresh_from_db
    DR.run_id == self.run_id,
  File "/home/app/airflow_venv/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 3500, in one
    raise orm_exc.NoResultFound("No row was found for one()")
sqlalchemy.orm.exc.NoResultFound: No row was found for one()
```
airflow/models/dagrun.py
self,
        unfinished_tasks: List[TI],
        finished_tasks: List[TI],
        session: Session,
    ) -> bool:
        
        
        for ut in unfinished_tasks:
            if ut.are_dependencies_met(
                dep_context=DepContext(
                    flag_upstream_failed=True,
                    ignore_in_retry_period=True,
                    ignore_in_reschedule_period=True,
                    finished_tasks=finished_tasks,
                ),
                session=session,
            ):
                return True
        return False
    def _emit_true_scheduling_delay_stats_for_finished_state(self, finished_tis):
        """
        This is a helper method to emit the true scheduling delay stats, which is defined as
        the time when the first task in DAG starts minus the expected DAG run datetime.
        This method will be used in the update_state method when the state of the DagRun
        is updated to a completed status (either success or failure). The method will find the first
        started task within the DAG and calculate the expected DagRun start time (based on
        dag.execution_date & dag.schedule_interval), and minus these two values to get the delay.