**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
'asana': asana,
    'celery': celery,
    'cloudant': cloudant,
    'cncf.kubernetes': kubernetes,
    'databricks': databricks,
    'datadog': datadog,
    'dingding': [],
    'discord': [],
    'docker': docker,
    'elasticsearch': elasticsearch,
    'exasol': exasol,
    'facebook': facebook,
    'ftp': [],
    'google': google,
    'grpc': grpc,
    'hashicorp': hashicorp,
    'http': http,
    'imap': [],
    'influxdb': influxdb,
    'jdbc': jdbc,
    'jenkins': jenkins,
    'jira': jira,
    'microsoft.azure': azure,
    'microsoft.mssql': mssql,
    'microsoft.psrp': psrp,
    'microsoft.winrm': winrm,
    'mongo': mongo,
    'mysql': mysql,
    'neo4j': neo4j,
    'odbc': odbc,