In order to connect to virtual machine instances, the Nova platform needs to know your ssh public key.
You can display the list of availables ssh keys with the command
$ openstack keypair list
If you just authentificate for the first time, it’s normal that no keys display: you have not upload one yet.
Please upload your public ssh key as follows
$ openstack keypair create --public-key ~/.ssh/id_rsa_nova.pub tascan-rsa
+-------------+-------------------------------------------------+
| Field       | Value                                           |
+-------------+-------------------------------------------------+
| fingerprint | 9e:33:58:35:62:df:be:4b:47:4b:ba:bc:0e:8d:d9:26 |
| name        | tascan-rsa                                      |
| user_id     | b8b092a17bce4974b0cbd83179014f01                |
+-------------+-------------------------------------------------+
This time, when we list the availables keys, your key appear.
$ openstack keypair list
+------------+-------------------------------------------------+
| Name       | Fingerprint                                     |
+------------+-------------------------------------------------+
| tascan-rsa | 9e:33:58:35:62:df:be:4b:47:4b:ba:bc:0e:8d:d9:26 |
+------------+-------------------------------------------------+