# Error while attempting to disable login

**Apache Airflow version**: 2.0.0
**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**:

- **Cloud provider or hardware configuration**: mac-pro
- **OS** (e.g. from /etc/os-release): osx
- **Kernel** (e.g. `uname -a`): Darwin C02CW1JLMD6R 19.6.0 Darwin Kernel Version 19.6.0: Mon Aug 31 22:12:52 PDT 2020; root:xnu-6153.141.2~1/RELEASE_X86_64 x86_64
- **Install tools**:
- **Others**:

**What happened**:

When setting in `webserver_config.py`,
```python
AUTH_ROLE_PUBLIC = 'Admin'
```

Got error on webserver, when going to localhost:8080/home,
```log
[2020-12-17 16:29:09,993] {app.py:1891} ERROR - Exception on /home [GET]
Traceback (most recent call last):
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/airflow/www/auth.py", line 34, in decorated
    return func(*args, **kwargs)
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/airflow/www/views.py", line 540, in index
    user_permissions = current_app.appbuilder.sm.get_all_permissions_views()
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/airflow/www/security.py", line 226, in get_all_permissions_views
    for role in self.get_user_roles():
  File "/Users/Zshot0831/.local/share/virtualenvs/airflow_2-DimIlKMl/lib/python3.8/site-packages/airflow/www/security.py", line 219, in get_user_roles
    public_role = current_app.appbuilder.config.get('AUTH_ROLE_PUBLIC')
AttributeError: 'AirflowAppBuilder' object has no attribute 'config'
```


**What you expected to happen**:

Reached homepage without the need for authentication as admin.

**How to reproduce it**:
1. Install airflow in a new environment (or to a new directory, set env AIRFLOW_HOME=[my new dir])
2. Uncomment and change in webserver_config.py 
    ```python
    AUTH_ROLE_PUBLIC = 'Admin'
    ```
3. Start `airflow webserver`
4. Look in localhost:8080/home or localhost:8080

*webserver_config.py file**
```python
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
"""Default configuration for the Airflow webserver"""
import os

from flask_appbuilder.security.manager import AUTH_DB

# from flask_appbuilder.security.manager import AUTH_LDAP
# from flask_appbuilder.security.manager import AUTH_OAUTH
# from flask_appbuilder.security.manager import AUTH_OID
# from flask_appbuilder.security.manager import AUTH_REMOTE_USER


basedir = os.path.abspath(os.path.dirname(__file__))

# Flask-WTF flag for CSRF
WTF_CSRF_ENABLED = True

# ----------------------------------------------------
# AUTHENTICATION CONFIG
# ----------------------------------------------------
# For details on how to set up each of the following authentication, see
# http://flask-appbuilder.readthedocs.io/en/latest/security.html# authentication-methods
# for details.

# The authentication type
# AUTH_OID : Is for OpenID
# AUTH_DB : Is for database
# AUTH_LDAP : Is for LDAP
# AUTH_REMOTE_USER : Is for using REMOTE_USER from web server
# AUTH_OAUTH : Is for OAuth
AUTH_TYPE = AUTH_DB

# Uncomment to setup Full admin role name
# AUTH_ROLE_ADMIN = 'Admin'

# Uncomment to setup Public role name, no authentication needed
AUTH_ROLE_PUBLIC = 'Admin'

# Will allow user self registration
# AUTH_USER_REGISTRATION = True

# The default user self registration role
# AUTH_USER_REGISTRATION_ROLE = "Public"

# When using OAuth Auth, uncomment to setup provider(s) info
# Google OAuth example:
# OAUTH_PROVIDERS = [{
#   'name':'google',
#     'token_key':'access_token',
#     'icon':'fa-google',
#         'remote_app': {
#             'api_base_url':'https://www.googleapis.com/oauth2/v2/',
#             'client_kwargs':{
#                 'scope': 'email profile'
#             },
#             'access_token_url':'https://accounts.google.com/o/oauth2/token',
#             'authorize_url':'https://accounts.google.com/o/oauth2/auth',
#             'request_token_url': None,
#             'client_id': GOOGLE_KEY,
#             'client_secret': GOOGLE_SECRET_KEY,
#         }
# }]

# When using LDAP Auth, setup the ldap server
# AUTH_LDAP_SERVER = "ldap://ldapserver.new"

# When using OpenID Auth, uncomment to setup OpenID providers.
# example for OpenID authentication
# OPENID_PROVIDERS = [
#    { 'name': 'Yahoo', 'url': 'https://me.yahoo.com' },
#    { 'name': 'AOL', 'url': 'http://openid.aol.com/<username>' },
#    { 'name': 'Flickr', 'url': 'http://www.flickr.com/<username>' },
#    { 'name': 'MyOpenID', 'url': 'https://www.myopenid.com' }]

# ----------------------------------------------------
# Theme CONFIG
# ----------------------------------------------------
# Flask App Builder comes up with a number of predefined themes
# that you can use for Apache Airflow.
# http://flask-appbuilder.readthedocs.io/en/latest/customizing.html#changing-themes
# Please make sure to remove "navbar_color" configuration from airflow.cfg
# in order to fully utilize the theme. (or use that property in conjunction with theme)
# APP_THEME = "bootstrap-theme.css"  # default bootstrap
# APP_THEME = "amelia.css"
# APP_THEME = "cerulean.css"
# APP_THEME = "cosmo.css"
# APP_THEME = "cyborg.css"
# APP_THEME = "darkly.css"
# APP_THEME = "flatly.css"
# APP_THEME = "journal.css"
# APP_THEME = "lumen.css"
# APP_THEME = "paper.css"
# APP_THEME = "readable.css"
# APP_THEME = "sandstone.css"
# APP_THEME = "simplex.css"
# APP_THEME = "slate.css"
# APP_THEME = "solar.css"
# APP_THEME = "spacelab.css"
# APP_THEME = "superhero.css"
# APP_THEME = "united.css"
# APP_THEME = "yeti.css"
```

![Screen Shot 2020-12-17 at 4 37 06 PM](https://user-images.githubusercontent.com/3694482/102546943-64733800-4086-11eb-8dd7-6a36b2b8ee82.png)

airflow/www/security.py
"""
        Admin should have all the permission-views, except the dag views.
        because Admin already has Dags permission.
        Add the missing ones to the table for admin.
        :return: None.
        """
        dag_pvs = (
            self.get_session.query(sqla_models.ViewMenu)
            .filter(sqla_models.ViewMenu.name.like(f"{permissions.RESOURCE_DAG_PREFIX}%"))
            .all()
        )
        pv_ids = [pv.id for pv in dag_pvs]
        pvms = (
            self.get_session.query(sqla_models.PermissionView)
            .filter(~sqla_models.PermissionView.view_menu_id.in_(pv_ids))
            .all()
        )
        pvms = [p for p in pvms if p.permission and p.view_menu]
        admin = self.find_role('Admin')
        admin.permissions = list(set(admin.permissions) | set(pvms))
        self.get_session.commit()
    def sync_roles(self):