Keypair signing does not work when rebasing URL

[specialcircumstances]

With some reference to: Keypair generation does not work when rebasing URL - Issue #840

Issue type: URI resolution

Python version: 2.7.5
NetBox version: 1.9.2

I have a couple of instances of Netbox running, and to seperate them I rebase them behind nginx locations and use BASE_PATH = 'instancexx/'
e.g.
/opt/netbox/instance/instance01 ->> mynetboxserver/instance01
/opt/netbox/instance/instance01 ->> mynetboxserver/instance02

Similarly to issue #840 when signing a user key, after submitting the administrators private key, I would expect the URL to be:

https://mynetboxserver/instance01/admin/secrets/userkey/

but the request is for:

https://mynetboxserver/admin/secrets/userkey/

which of course does not work.