**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
#
#
#
"""Setup.py for the Airflow project."""
import glob
import logging
import os
import subprocess
import sys
import unittest
from copy import deepcopy
from os.path import dirname, relpath
from textwrap import wrap
from typing import Dict, List
from setuptools import Command, Distribution, find_namespace_packages, setup
from setuptools.command.develop import develop as develop_orig
from setuptools.command.install import install as install_orig
from distutils import log  
INSTALL_PROVIDERS_FROM_SOURCES = 'INSTALL_PROVIDERS_FROM_SOURCES'
PY39 = sys.version_info >= (3, 9)
logger = logging.getLogger(__name__)
version = '2.3.0.dev0'
my_dir = dirname(__file__)
def airflow_test_suite() -> unittest.TestSuite:
    """Test suite for Airflow tests"""
    test_loader = unittest.TestLoader()
    test_suite = test_loader.discover(os.path.join(my_dir, 'tests'), pattern='test_*.py')
    return test_suite
class CleanCommand(Command):