**Apache Airflow version**: 2.0.1

**Environment**:

- **Cloud provider or hardware configuration**: AWS

**What happened**:
I have Airflow with Cloudwatch-based remote logging running. I also have `BashOperator` that does, for example, `rsync` with invalid parameters, for example `rsync -av test test`. The output of the `rsync` error is formatted and contains empty line. Once that empty line is logged to the Cloudwatch, i receive an error:
```
2021-04-06 19:29:22,318] /home/airflow/.local/lib/python3.6/site-packages/watchtower/__init__.py:154 WatchtowerWarning: Failed to deliver logs: Parameter validation failed:
Invalid length for parameter logEvents[5].message, value: 0, valid range: 1-inf
[2021-04-06 19:29:22,320] /home/airflow/.local/lib/python3.6/site-packages/watchtower/__init__.py:158 WatchtowerWarning: Failed to deliver logs: None
```

So basically empty lines can't be submitted to the Cloudwatch and as result the whole output of the process doesn't appear in logs.

**What you expected to happen**:

I expect to have an output of the bash command in logs. Empty lines can be skipped or replaced with something.

**How to reproduce it**:

For example: run `BashOperator` with `rsync` command that fails on Airflow with Cloudwatch-based remote logging. It could be any other command that produces empty line in the output.
setup.py
]
winrm = [
    'pywinrm~=0.4',
]
yandex = [
    'yandexcloud>=0.97.0',
]
zendesk = [
    'zdesk',
]
mypy_dependencies = [
    'mypy==0.910',
    'types-croniter',
    'types-docutils',
    'types-freezegun',
    'types-paramiko',
    'types-protobuf',
    'types-python-dateutil',
    'types-python-slugify',
    'types-pytz',
    'types-redis',
    'types-requests',
    'types-setuptools',
    'types-termcolor',
    'types-tabulate',
    'types-Markdown',
    'types-PyMySQL',
    'types-PyYAML',
]
devel_only = [