**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.
airflow/providers/amazon/aws/log/cloudwatch_task_handler.py
#
#
#
from datetime import datetime
import watchtower
try:
    from functools import cached_property
except ImportError:
    from cached_property import cached_property
from airflow.configuration import conf
from airflow.utils.log.file_task_handler import FileTaskHandler
from airflow.utils.log.logging_mixin import LoggingMixin
class CloudwatchTaskHandler(FileTaskHandler, LoggingMixin):
    """
    CloudwatchTaskHandler is a python log handler that handles and reads task instance logs.
    It extends airflow FileTaskHandler and uploads to and reads from Cloudwatch.
    :param base_log_folder: base folder to store logs locally
    :type base_log_folder: str
    :param log_group_arn: ARN of the Cloudwatch log group for remote log storage
        with format ``arn:aws:logs:{region name}:{account id}:log-group:{group name}``
    :type log_group_arn: str
    :param filename_template: template for file name (local storage) or log stream name (remote)
    :type filename_template: str
    """
    def __init__(self, base_log_folder: str, log_group_arn: str, filename_template: str):