openstack_nova_quota* metrics are not working due to possible issues in caching or, the way they are registered and collected.

In cache mode (enable --cache) the log shows:

level=ERROR source=utils.go:83 msg="Create gather failed" cloud=openstack service=compute error="168 error(s) occurred:\n* collected metric \"openstack_nova_quota_cores\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"in_use\"} gauge:{value:0}} was collected before with the same name and label values\n* collected metric \"openstack_nova_quota_cores\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"reserved\"} gauge:{value:0}} was collected before with the same name and label values\n* collected metric \"openstack_nova_quota_cores\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"limit\"} gauge:{value:20}} was collected before with the same name and label values\n* collected metric \"openstack_nova_quota_instances\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"in_use\"} gauge:{value:0}} was collected before with the same name and label values\n* collected metric \"openstack_nova_quota_instances\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"reserved\"} gauge:{value:0}} was collected before with the same name and label values\n* collected metric \"openstack_nova_quota_instances\" { label:{name:\"tenant\" value:\"alt_demo\"} label:{name:\"type\" value:\"limit\"} gauge:{value:10}} was collected before with the same name and label values\n...

Metrics in this log are not exhausted. With this, there is no openstack_nova* metrics output, not only the openstack_nova_quota* ones.

In non-cache mode, same error happens and block everything when querying metrics:

An error has occurred while serving metrics:

168 error(s) occurred:
* collected metric "openstack_nova_quota_cores" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"in_use"} gauge:{value:0}} was collected before with the same name and label values
* collected metric "openstack_nova_quota_cores" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"reserved"} gauge:{value:0}} was collected before with the same name and label values
* collected metric "openstack_nova_quota_cores" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"limit"} gauge:{value:20}} was collected before with the same name and label values
* collected metric "openstack_nova_quota_instances" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"in_use"} gauge:{value:0}} was collected before with the same name and label values
* collected metric "openstack_nova_quota_instances" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"reserved"} gauge:{value:0}} was collected before with the same name and label values
* collected metric "openstack_nova_quota_instances" { label:{name:"tenant" value:"alt_demo"} label:{name:"type" value:"limit"} gauge:{value:10}} was collected before with the same name and label values
...