Unhelpful error message on creating a space with a key that already exists

Steps to repeat:

1. As user1 with system administration privileges, but not in the confluence-administrators group or confluence-users group, create a space with key 'FOO'. This leads to a space with default permissions of confluence-users with some permissions, and user1 as the administrator.
2. As user2 with system administration privileges, but not in the confluence-administrators group or confluence-users group, create a space with key 'FOO'. First, note that space 'FOO' does not appear in the list of visible spaces for user2.

You'll receive an error stating that "You do not have permissions for this operation."

This is somewhat related to CONF-4616 and CONF-9382 in that not using the hardwired confluence-administrators or confluence-users group leads to system administrators not actually having all the rights of a confluence-administrator.