**Apache Airflow version**:
2.1.0

**What happened**:
When printing emoji to a DAG log, the Airflow dashboard fails to display the entire log.
When checking the output log in the Airflow dashboard, the following error message appears:

> *** Failed to load local log file: /tmp/dag_name/task_name/2021-07-06T10:49:18.136953+00:00/1.log
> *** 'ascii' codec can't decode byte 0xf0 in position 3424: ordinal not in range(128)

**What you expected to happen**:
The log should be displayed.

<!-- What do you think went wrong? -->


**How to reproduce it**:
Insert the following into any Python DAG, then run it.
`print("💼")`

**How often does this problem occur?**
Every log with an emoji in it prints an error.

**Why would anyone even want to print emoji in their logs?**
When they're part of the dataset you're processing.
airflow/utils/log/file_task_handler.py
name=ti.hostname,
                    namespace=conf.get('kubernetes', 'namespace'),
                    container='base',
                    follow=False,
                    tail_lines=100,
                    _preload_content=False,
                )
                for line in res:
                    log += line.decode()
            except Exception as f:
                log += f'*** Unable to fetch logs from worker pod {ti.hostname} ***\n{str(f)}\n\n'
        else:
            url = os.path.join("http://{ti.hostname}:{worker_log_server_port}/log", log_relative_path).format(
                ti=ti, worker_log_server_port=conf.get('logging', 'WORKER_LOG_SERVER_PORT')
            )
            log += f"*** Log file does not exist: {location}\n"
            log += f"*** Fetching from: {url}\n"
            try:
                timeout = None  
                try:
                    timeout = conf.getint('webserver', 'log_fetch_timeout_sec')
                except (AirflowConfigException, ValueError):
                    pass
                signer = TimedJSONWebSignatureSerializer(
                    secret_key=conf.get('webserver', 'secret_key'),
                    algorithm_name='HS512',
                    expires_in=conf.getint('webserver', 'log_request_clock_grace', fallback=30),
                    
                    salt='task-instance-logs',
                )