**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-api-core>=1.25.1,<3.0.0',
    'google-api-python-client>=1.6.0,<2.0.0',
    
    
    
    'google-auth>=1.0.0,<3.0.0',
    'google-auth-httplib2>=0.0.1',
    'google-cloud-automl>=2.1.0,<3.0.0',
    'google-cloud-bigquery-datatransfer>=3.0.0,<4.0.0',
    'google-cloud-bigtable>=1.0.0,<2.0.0',
    'google-cloud-build>=3.0.0,<4.0.0',
    'google-cloud-container>=0.1.1,<2.0.0',
    'google-cloud-datacatalog>=3.0.0,<4.0.0',
    'google-cloud-dataproc>=3.1.0,<4.0.0',
    'google-cloud-dataproc-metastore>=1.2.0,<2.0.0',
    'google-cloud-dlp>=0.11.0,<2.0.0',
    'google-cloud-kms>=2.0.0,<3.0.0',
    'google-cloud-language>=1.1.1,<2.0.0',
    'google-cloud-logging>=2.1.1,<3.0.0',
    
    
    'google-cloud-memcache>=0.2.0,<1.1.0',
    'google-cloud-monitoring>=2.0.0,<3.0.0',
    'google-cloud-os-login>=2.0.0,<3.0.0',
    'google-cloud-pubsub>=2.0.0,<3.0.0',
    'google-cloud-redis>=2.0.0,<3.0.0',
    'google-cloud-secret-manager>=0.2.0,<2.0.0',
    'google-cloud-spanner>=1.10.0,<2.0.0',