Comment 25 for bug 1805332

The package from rocky-proposed worked for me. Version info below:
python3-glance-store:
  Installed: 0.26.1-0ubuntu2.1~cloud0
  Candidate: 0.26.1-0ubuntu2.1~cloud0
  Version table:
 *** 0.26.1-0ubuntu2.1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-proposed/rocky/main amd64 Packages
        100 /var/lib/dpkg/status
     0.26.1-0ubuntu2~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/rocky/main amd64 Packages
     0.23.0-0ubuntu1 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

Test output:

$ openstack image create --public --file /home/ubuntu/images/bionic-server-cloudimg-amd64.img bionic-test
500 Internal Server Error: The server has either erred or is incapable of performing the requested operation. (HTTP 500)

$ juju run --unit glance/0 "apt-cache policy python3-glance-store"
python3-glance-store:
  Installed: 0.26.1-0ubuntu2~cloud0
  Candidate: 0.26.1-0ubuntu2~cloud0
  Version table:
 *** 0.26.1-0ubuntu2~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/rocky/main amd64 Packages
        100 /var/lib/dpkg/status
     0.23.0-0ubuntu1 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

$ juju run --unit glance/0 "add-apt-repository cloud-archive:rocky-proposed --yes --update"
...
$ juju run --unit glance/0 "apt install --yes python3-glance-store; systemctl restart glance-api"
...
(clients) ubuntu@gnuoy-bastion2:~/branches/nova-compute$ juju run --unit glance/0 "apt-cache policy python3-glance-store"
python3-glance-store:
  Installed: 0.26.1-0ubuntu2.1~cloud0
  Candidate: 0.26.1-0ubuntu2.1~cloud0
  Version table:
 *** 0.26.1-0ubuntu2.1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-proposed/rocky/main amd64 Packages
        100 /var/lib/dpkg/status
     0.26.1-0ubuntu2~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/rocky/main amd64 Packages
     0.23.0-0ubuntu1 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

$ openstack image create --public --file /home/ubuntu/images/bionic-server-cloudimg-amd64.img bionic-test
+------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field | Value |
+------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| checksum | c8994590c7d61dc68922e461686ef936 |
| container_format | bare |
| created_at | 2019-05-22T07:41:28Z |
| disk_format | raw |
| file | /v2/images/788db968-ea48-4b4f-8c91-4e15d23dbe4c/file |
| id | 788db968-ea48-4b4f-8c91-4e15d23dbe4c |
| min_disk | 0 |
| min_ram | 0 |
| name | bionic-test |
| owner | 3d4ca9d5799546bd852db00ee6d5d4c0 |
| properties | os_hash_algo='sha512', os_hash_value='be4993640deb7eb99b07667213b1fe3a9145df2c0ed5c72cf786a621fe64e93fb543cbb3fafa9a130988b684da432d2a55493c50e77a9dfe336e7ed996be92d9', os_hidden='False' |
| protected | False |
| schema | /v2/schemas/image |
| size | 348127232 |
| status | active |
| tags | |
| updated_at | 2019-05-22T07:41:46Z |
| virtual_size | None |
| visibility | public |
+------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+