When I run python manage.py startapp appname, the TypeError in the subject of this issue is thrown.
Solution
I realized that in the settings.py file, had this line:
DATABASES['default'].update(dj_database_url.config(conn_max_age=500, require_ssl=True))
The require_ssl argument is actually supposed to be ssl_require basing on the the config() function in dj_database_url.py file of the dj-database-url package.