Error on removing hosts/disks

on command:

`curl --insecure --user admin:admin -d "ip_address=10.0.36.21" -X DELETE http://127.0.0.1:5000/api/client/iqn.1998-01.com.vmware:internal-appliances-hv-01-4b798644 > test.html`

> Array
(
[language] => pytb
[code] => Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/usr/bin/rbd-target-api", line 94, in decorated
return f(*args, **kwargs)
File "/usr/bin/rbd-target-api", line 961, in client
gateways.remove(local_gw)
ValueError: list.remove(x): x not in list
)
failed 2

I had problems with the server being messed up after multiple compiles and tests, now I want to remove all old gateways that do not exist anymore. Before I can do that I have to remove those disks and hosts, but then this error came.