**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
'sphinxcontrib-httpdomain>=1.7.0',
    'sphinxcontrib-redoc>=1.6.0',
    'sphinxcontrib-spelling==7.2.1',
]
docker = [
    'docker>=5.0.3',
]
drill = ['sqlalchemy-drill>=1.1.0', 'sqlparse>=0.4.1']
druid = [
    'pydruid>=0.4.1',
]
elasticsearch = [
    'elasticsearch>7',
    'elasticsearch-dbapi',
    'elasticsearch-dsl>=5.0.0',
]
exasol = ['pyexasol>=0.5.1,<1.0.0', pandas_requirement]
facebook = [
    'facebook-business>=6.0.2',
]
flask_appbuilder_authlib = [
    'authlib',
]
google = [
    'PyOpenSSL',
    
    
    
    'google-ads>=12.0.0,<14.0.1',