**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
'pytest-rerunfailures~=9.1',
    'pytest-timeouts',
    'pytest-xdist',
    'python-jose',
    'pywinrm',
    'qds-sdk>=1.9.6',
    'pytest-httpx',
    'requests_mock',
    'semver',
    'wheel',
    'yamllint',
]
devel = cgroups + devel_only + doc + kubernetes + mypy_dependencies + mysql + pandas + password
devel_hadoop = devel + hdfs + hive + kerberos + presto + webhdfs
PROVIDERS_REQUIREMENTS: Dict[str, List[str]] = {
    'airbyte': http_provider,
    'alibaba': alibaba,
    'amazon': amazon,
    'apache.beam': apache_beam,
    'apache.cassandra': cassandra,
    'apache.drill': drill,
    'apache.druid': druid,
    'apache.hdfs': hdfs,
    'apache.hive': hive,
    'apache.kylin': kylin,
    'apache.livy': http_provider,
    'apache.pig': [],
    'apache.pinot': pinot,
    'apache.spark': spark,
    'apache.sqoop': [],