**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
]
pandas = [
    pandas_requirement,
]
papermill = [
    'papermill[all]>=1.2.1',
    'scrapbook[all]',
]
password = [
    'bcrypt>=2.0.0',
    'flask-bcrypt>=0.7.1',
]
pinot = [
    
    
    'pinotdb>0.1.2,<1.0.0',
]
plexus = [
    'arrow>=0.16.0',
]
postgres = [
    'psycopg2-binary>=2.7.4',
]
presto = [
    'presto-python-client>=0.7.0,<0.8',
    pandas_requirement,
]
psrp = [
    'pypsrp~=0.5',
]