**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
'google-cloud-speech>=0.36.3,<2.0.0',
    'google-cloud-storage>=1.30,<2.0.0',
    'google-cloud-tasks>=2.0.0,<3.0.0',
    'google-cloud-texttospeech>=0.4.0,<2.0.0',
    'google-cloud-translate>=1.5.0,<2.0.0',
    'google-cloud-videointelligence>=1.7.0,<2.0.0',
    'google-cloud-vision>=0.35.2,<2.0.0',
    'google-cloud-workflows>=0.1.0,<2.0.0',
    'grpcio-gcp>=0.2.2',
    'httpx',
    'json-merge-patch~=0.2',
    
    
    'pandas-gbq<0.15.0',
    pandas_requirement,
]
grpc = [
    'google-auth>=1.0.0, <3.0.0',
    'google-auth-httplib2>=0.0.1',
    'grpcio>=1.15.0',
]
hashicorp = [
    'hvac~=0.10',
]
hdfs = [
    'snakebite-py3',
    'hdfs[avro,dataframe,kerberos]>=2.0.4',
]
hive = [
    'hmsclient>=0.1.0',