Introspection fails with ERROR ironic_inspector.main KeyError: 'JSONIFY_MIMETYPE' in Red Hat OpenStack Platform 13

Issue

Introspection fails with ERROR ironic_inspector.main KeyError: 'JSONIFY_MIMETYPE' in Red Hat OpenStack Platform 13.

The ironic logs show:

2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main [req-6568c9f5-0016-4572-8881-76738215c86b - - - - -] Internal server error: KeyError: 'JSONIFY_MIMETYPE'
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main Traceback (most recent call last):
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/ironic_inspector/main.py", line 76, in wrapper
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main     return func(*args, **kwargs)
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/ironic_inspector/main.py", line 182, in wrapper
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main     return func(*args, **kwargs)
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/ironic_inspector/main.py", line 200, in api_root
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main     return flask.jsonify(versions=versions)
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/json/__init__.py", line 322, in jsonify
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main     mimetype=current_app.config['JSONIFY_MIMETYPE']
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main KeyError: 'JSONIFY_MIMETYPE'
2019-04-22 22:31:53.200 8179 ERROR ironic_inspector.main 
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main [req-6568c9f5-0016-4572-8881-76738215c86b - - - - -] Exception on / [GET]: KeyError: 'JSONIFY_MIMETYPE'
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main Traceback (most recent call last):
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     response = self.full_dispatch_request()
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     rv = self.handle_user_exception(e)
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     reraise(exc_type, exc_value, tb)
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     rv = self.dispatch_request()
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     return self.view_functions[rule.endpoint](**req.view_args)
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/ironic_inspector/main.py", line 86, in wrapper
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     return error_response(msg)
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/ironic_inspector/main.py", line 66, in error_response
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     res = flask.jsonify(error={'message': str(exc)})
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main   File "/usr/lib/python2.7/site-packages/flask/json/__init__.py", line 322, in jsonify
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main     mimetype=current_app.config['JSONIFY_MIMETYPE']
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main KeyError: 'JSONIFY_MIMETYPE'
2019-04-22 22:31:53.202 8179 ERROR ironic_inspector.main