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.
airflow/utils/log/secrets_masker.py
#
#
"""Mask sensitive information from logs"""
import collections
import logging
import re
from typing import TYPE_CHECKING, Iterable, Optional, Set, TypeVar, Union
from airflow.compat.functools import cache, cached_property
if TYPE_CHECKING:
    from airflow.typing_compat import RePatternType
    RedactableItem = TypeVar('RedctableItem')
DEFAULT_SENSITIVE_FIELDS = frozenset(
    {
        'password',
        'secret',
        'passwd',
        'authorization',
        'api_key',
        'apikey',
        'access_token',
    }
)
"""Names of fields (Connection extra, Variable key name etc.) that are deemed sensitive"""
@cache
def get_sensitive_variables_fields():