Juniper dev.provision error: Unknown MySQL server host 'edx.devstack.mysql57'

I checked out juniper.master branch followed by steps of
created virtual env
set OPENEDX_RELEASE=juniper.master
make dev.checkout
make requirements
make dev.clone
make dev.pull
make dev.provision

During the dev.provision step, it gives the following error.

File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/db/backends/base/", line 217, in ensure_connection
edx.devstack.lms          |     self.connect()
edx.devstack.lms          |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/db/backends/base/", line 195, in connect
edx.devstack.lms          |     self.connection = self.get_new_connection(conn_params)
edx.devstack.lms          |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/db/backends/mysql/", line 227, in get_new_connection
edx.devstack.lms          |     return Database.connect(**conn_params)
edx.devstack.lms          |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/MySQLdb/", line 130, in Connect
edx.devstack.lms          |     return Connection(*args, **kwargs)
edx.devstack.lms          |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/MySQLdb/", line 185, in __init__
edx.devstack.lms          |     super().__init__(*args, **kwargs2)
edx.devstack.lms          | MySQLdb._exceptions.OperationalError: (2005, "Unknown MySQL server host 'edx.devstack.mysql57' (22)"

Any help would be appreciated.

there should be a problem with the checkout step.
juniper does not have/need a mysql57 machine.
so I think your edx-platform is not on any of juniper branches.