**Apache Airflow version**:
2.0.1

**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**:

- **Cloud provider or hardware configuration**: 4GB RAM, Processor - Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
- **OS** (e.g. from /etc/os-release): 18.04.5 LTS (Bionic Beaver)
- **Kernel** (e.g. `uname -a`): Linux 4.15.0-136-generic
- **Install tools**: bare metal installation as per commands given [here](https://airflow.apache.org/docs/apache-airflow/stable/installation.html)

**What happened**:

On running `airflow scheduler -p` got following error:-
```
Traceback (most recent call last):
  File "/home/vineet/Documents/projects/venv/bin/airflow", line 8, in <module>
    sys.exit(main())
  File "/home/vineet/Documents/projects/venv/lib/python3.6/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/home/vineet/Documents/projects/venv/lib/python3.6/site-packages/airflow/cli/cli_parser.py", line 48, in command
    return func(*args, **kwargs)
  File "/home/vineet/Documents/projects/venv/lib/python3.6/site-packages/airflow/utils/cli.py", line 86, in wrapper
    metrics = _build_metrics(f.__name__, args[0])
  File "/home/vineet/Documents/projects/venv/lib/python3.6/site-packages/airflow/utils/cli.py", line 118, in _build_metrics
    full_command[idx + 1] = "*" * 8
IndexError: list assignment index out of range
```
As per docs, `-p` flag is a valid flag and gives correct result for `airflow scheduler --do-pickle`

**How to reproduce it**:
Install `airflow` 2.0.1 and run `airflow scheduler -p`
airflow/utils/cli.py
"""Fetch DAG from the database using pickling"""
    from airflow.models import DagPickle
    dag_pickle = session.query(DagPickle).filter(DagPickle.id == pickle_id).first()
    if not dag_pickle:
        raise AirflowException("Who hid the pickle!? [missing pickle]")
    pickle_dag = dag_pickle.pickle
    return pickle_dag
def setup_locations(process, pid=None, stdout=None, stderr=None, log=None):
    """Creates logging paths"""
    if not stderr:
        stderr = os.path.join(settings.AIRFLOW_HOME, f'airflow-{process}.err')
    if not stdout:
        stdout = os.path.join(settings.AIRFLOW_HOME, f'airflow-{process}.out')
    if not log:
        log = os.path.join(settings.AIRFLOW_HOME, f'airflow-{process}.log')
    if not pid:
        pid = os.path.join(settings.AIRFLOW_HOME, f'airflow-{process}.pid')
    else:
        pid = os.path.abspath(pid)
    return pid, stdout, stderr, log
def setup_logging(filename):
    """Creates log file handler for daemon process"""
    root = logging.getLogger()
    handler = logging.FileHandler(filename)
    formatter = logging.Formatter(settings.SIMPLE_LOG_FORMAT)
    handler.setFormatter(formatter)
    root.addHandler(handler)
    root.setLevel(settings.LOGGING_LEVEL)
    return handler.stream
def sigint_handler(sig, frame):