Comment 18 for bug 1951182

I'm trying to upgrade project from bionic, I got same issue
as the upgrade purpose, I have to use old juju version

```
$ juju deploy ./config/bundle.yaml

- deploy application neutron-api on bionic using cs:neutron-api-304
ERROR cannot deploy bundle: cs:neutron-api-304 resource "policyd-override": bad metadata: resource missing filename

$ juju --version
2.8.13-bionic-amd64

# bundle.yaml
series: bionic

machines:
  "1001":
    constraints: tags=ctrl001
  "1005":
    constraints: tags=hci
  "1006":
    constraints: tags=ctrl002
  "1007":
    constraints: tags=hci
  "1008":
    constraints: tags=ctrl003

applications:
  neutron-api:
    charm: cs:neutron-api
    num_units: 3
    bindings:
      "": *oam-space
      public: *public-space
      admin: *admin-space
      internal: *internal-space
      shared-db: *internal-space
    options:
      worker-multiplier: *worker-multiplier
      openstack-origin: *openstack-origin
      region: *openstack-region
      flat-network-providers: physnet1
      vlan-ranges:
      neutron-security-groups: True
      overlay-network-type: vxlan
      use-internal-endpoints: True
      vip: *neutron-api-vip
      enable-l3ha: False
      enable-dvr: True
      dhcp-agents-per-network: 2
      enable-ml2-port-security: True
      default-tenant-network-type: vxlan
      l2-population: True
      enable-ml2-dns: True
      dns-domain: *dns-domain
      reverse-dns-lookup: True
      ipv4-ptr-zone-prefix-size: *dns-cidr
      global-physnet-mtu: 1550
      path-mtu: 1550
      physical-network-mtus: physnet1:1500
    to:
    - lxd:1001
    - lxd:1006
    - lxd:1008

```
not working while change `cs` to `ch`
FROM: charm: cs:neutron-api
TO: charm: ch:neutron-api

```
$ juju deploy ./config/bundle.yaml
ERROR cannot deploy bundle: the provided bundle has the following errors:
invalid charm URL in application "neutron-api": cannot parse URL "ch:neutron-api": schema "ch" not valid
```

how to fix this issue?