**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
return f'.dev0+{sha}.dirty'
        
        return f'.release:{version_}+{sha}'
    return 'no_git_version'
def write_version(filename: str = os.path.join(*[my_dir, "airflow", "git_version"])) -> None:
    """
    Write the Semver version + git hash to file, e.g. ".dev0+2f635dc265e78db6708f59f68e8009abb92c1e65".
    :param str filename: Destination file to write
    """
    text = f"{git_version(version)}"
    with open(filename, 'w') as file:
        file.write(text)
pandas_requirement = 'pandas>=0.17.1, <2.0'
alibaba = [
    'oss2>=2.14.0',
]
amazon = [
    'boto3>=1.15.0,<1.19.0',
    'watchtower~=1.0.6',
    'jsonpath_ng>=1.5.3',
    'redshift_connector~=2.0.888',
    'sqlalchemy_redshift~=0.8.6',
    pandas_requirement,
]
apache_beam = [
    'apache-beam>=2.20.0',
]
asana = ['asana>=0.10']
async_packages = [
    'eventlet>= 0.9.7',