Discovered in this [Slack conversation](https://apache-airflow.slack.com/archives/CCQ7EGB1P/p1621752408213700).

When you have connections with empty passwords masking logs masks all the character breaks:
```
[2021-05-23 04:00:23,309] {{logging_mixin.py:104}} WARNING - ***-***-***-*** ***L***o***g***g***i***n***g*** ***e***r***r***o***r*** ***-***-***-***
[2021-05-23 04:00:23,309] {{logging_mixin.py:104}} WARNING - ***T***r***a***c***e***b***a***c***k*** ***(***m***o***s***t*** ***r***e***c***e***n***t*** ***c***a***l***l*** ***l***a***s***t***)***:***
[2021-05-23 04:00:23,309] {{logging_mixin.py:104}} WARNING - *** *** ***F***i***l***e*** ***"***/***u***s***r***/***l***o***c***a***l***/***l***i***b***/***p***y***t***h***o***n***3***.***8***/***l***o***g***g***i***n***g***/***_***_***i***n***i***t***_***_***.***p***y***"***,*** ***l***i***n***e*** ***1***0***8***1***,*** ***i***n*** ***e***m***i***t***
*** *** *** *** ***m***s***g*** ***=*** ***s***e***l***f***.***f***o***r***m***a***t***(***r***e***c***o***r***d***)***
```

Until this is fixed, an easy workaround is to disable masking via disabling sensitive connection masking in configuration:

```
[core]
hide_sensitive_var_conn_fields = False
```

or vial env variable:

```
AIRFLOW__CORE__HIDE_SENSITIVE_VAR_CONN_FIELDS="False"
```

This is only happening if the task accesses the connection that has empty password. However there are a number of cases where such an empty password might be "legitimate" - for example in `google` provider you might authenticate using env variable or workload identity and connection will contain an empty password then.
tests/utils/log/test_secrets_masker.py
def test_message(self, logger, caplog):
        logger.info("XpasswordY")
        assert caplog.text == "INFO X***Y\n"
    def test_args(self, logger, caplog):
        logger.info("Cannot connect to %s", "user:password")
        assert caplog.text == "INFO Cannot connect to user:***\n"
    def test_extra(self, logger, caplog):
        logger.handlers[0].formatter = ShortExcFormatter("%(levelname)s %(message)s %(conn)s")
        logger.info("Cannot connect", extra={'conn': "user:password"})
        assert caplog.text == "INFO Cannot connect user:***\n"
    def test_exception(self, logger, caplog):
        try:
            conn = "user:password"
            raise RuntimeError("Cannot connect to " + conn)
        except RuntimeError:
            logger.exception("Err")
        line = lineno() - 4
        assert caplog.text == textwrap.dedent(
            f"""\
            ERROR Err
            Traceback (most recent call last):
              File ".../test_secrets_masker.py", line {line}, in test_exception
                raise RuntimeError("Cannot connect to " + conn)
            RuntimeError: Cannot connect to user:***
            """
        )
    def test_exception_not_raised(self, logger, caplog):