Hello @kartik,
My settings.py did not have a HOST for MySQL database, but I needed to add one for PostgreSQL to work.
In my case, I added localhost to the HOST setting and it worked.
Here is the DATABASES section from my settings.py.
DATABASES = { 
    'default': { 
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': '<MYDATABASE>', 
        'USER': '<MYUSER>', 
        'PASSWORD': '<MYPASSWORD>', 
        'HOST': 'localhost', # the missing piece of the puzzle 
        'PORT': '', # optional, I don't need this since I'm using the standard port
    } 
}
Hope it helps!!
Thank you!!