You can check if a PO file is valid with the following command:

        msgfmt -c -o /dev/null <po file>
      

The following errors were found in nova 's PO files:

debconf: debian/nova-api.templates.in:4: Wrong input line:
 _Description: Set up a database for Nova API?
debconf: debian/nova-api.templates.in:5: Wrong input line:
  No database has been set up for Nova to use. If you want
debconf: debian/nova-api.templates.in:6: Wrong input line:
  to set one up now, please make sure you have all needed
debconf: debian/nova-api.templates.in:7: Wrong input line:
  information:
debconf: debian/nova-api.templates.in:8: Wrong input line:
  .
debconf: debian/nova-api.templates.in:9: Wrong input line:
   * the host name of the database server (which must allow TCP
debconf: debian/nova-api.templates.in:10: Wrong input line:
     connections from this machine);
debconf: debian/nova-api.templates.in:11: Wrong input line:
   * a username and password to access the database;
debconf: debian/nova-api.templates.in:12: Wrong input line:
   * the type of database management software you want to use.
debconf: debian/nova-api.templates.in:13: Wrong input line:
  .
debconf: debian/nova-api.templates.in:14: Wrong input line:
  If you don't choose this option, no database will be set up and Nova
debconf: debian/nova-api.templates.in:15: Wrong input line:
  will use regular SQLite support.
debconf: debian/nova-api.templates.in:16: Wrong input line:
  .
debconf: debian/nova-api.templates.in:17: Wrong input line:
  You can change this setting later on by running "dpkg-reconfigure
debconf: debian/nova-api.templates.in:18: Wrong input line:
  -plow nova-api".
podebconf: file debian/po/templates.pot not found
podebconf: file debian/po/POTFILES.in not found
debconf: debian/nova-common.templates.in:1: Wrong input line:
 # These templates have been reviewed by the debian-l10n-english
debconf: debian/nova-common.templates.in:2: Wrong input line:
 # team
debconf: debian/nova-common.templates.in:3: Wrong input line:
 #
debconf: debian/nova-common.templates.in:4: Wrong input line:
 # If modifications/additions/rewording are needed, please ask
debconf: debian/nova-common.templates.in:5: Wrong input line:
 # debian-l10n-english@lists.debian.org for advice.
debconf: debian/nova-common.templates.in:6: Wrong input line:
 #
debconf: debian/nova-common.templates.in:7: Wrong input line:
 # Even minor modifications require translation updates and such
debconf: debian/nova-common.templates.in:8: Wrong input line:
 # changes should be coordinated with translators and reviewers.
debconf: debian/nova-common.templates.in:12: Wrong input line:
 _Description: Value for my_ip:
debconf: debian/nova-common.templates.in:13: Wrong input line:
  This value will be stored in the my_ip directive of nova.conf.
debconf: debian/nova-common.templates.in:18: Wrong input line:
 _Description: Neutron server URL:
debconf: debian/nova-common.templates.in:19: Wrong input line:
  Please enter the URL of the Neutron server.
debconf: debian/nova-common.templates.in:24: Wrong input line:
 _Description: Neutron admin tenant name:
debconf: debian/nova-common.templates.in:25: Wrong input line:
  Nova needs to be able to communicate with Neutron through Keystone. Therefore
debconf: debian/nova-common.templates.in:26: Wrong input line:
  Nova needs to know the Neutron admin tenant, username and password.
debconf: debian/nova-common.templates.in:27: Wrong input line:
  .
debconf: debian/nova-common.templates.in:28: Wrong input line:
  Please enter the name of the admin tenant for Neutron.
debconf: debian/nova-common.templates.in:33: Wrong input line:
 _Description: Neutron administrator username:
debconf: debian/nova-common.templates.in:34: Wrong input line:
  Please enter the username of the Neutron administrator.
debconf: debian/nova-common.templates.in:38: Wrong input line:
 _Description: Neutron administrator password:
debconf: debian/nova-common.templates.in:39: Wrong input line:
  Please enter the password of the Neutron administrator.
debconf: debian/nova-common.templates.in:43: Wrong input line:
 _Description: Metadata proxy shared secret:
debconf: debian/nova-common.templates.in:44: Wrong input line:
  VM instances using Neutron to handle networking retrieve their metadata
debconf: debian/nova-common.templates.in:45: Wrong input line:
  through the Neutron metadata agent, which serves as a proxy to the Nova
debconf: debian/nova-common.templates.in:46: Wrong input line:
  metadata REST API server.
debconf: debian/nova-common.templates.in:47: Wrong input line:
  .
debconf: debian/nova-common.templates.in:48: Wrong input line:
  Please enter the password that should be used to protect communications
debconf: debian/nova-common.templates.in:49: Wrong input line:
  between the Neutron metadata proxy agent and the Nova metadata server. The
debconf: debian/nova-common.templates.in:50: Wrong input line:
  same shared password should be used when setting up the neutron-metadata-agent
debconf: debian/nova-common.templates.in:51: Wrong input line:
  package.
debconf: debian/nova-common.templates.in:56: Wrong input line:
 _Description: Cinder os region name:
debconf: debian/nova-common.templates.in:57: Wrong input line:
  Please enter the region name for cinder service.
debconf: debian/nova-common.templates.in:62: Wrong input line:
 _Description: Placement admin tenant name:
debconf: debian/nova-common.templates.in:63: Wrong input line:
  Nova needs to be able to communicate with Placement through Keystone. Therefore
debconf: debian/nova-common.templates.in:64: Wrong input line:
  Nova needs to know the Placement admin tenant, username and password.
debconf: debian/nova-common.templates.in:65: Wrong input line:
  .
debconf: debian/nova-common.templates.in:66: Wrong input line:
  Please enter the name of the admin tenant for Placement.
debconf: debian/nova-common.templates.in:71: Wrong input line:
 _Description: Placement administrator username:
debconf: debian/nova-common.templates.in:72: Wrong input line:
  Please enter the username of the Placement administrator.
debconf: debian/nova-common.templates.in:76: Wrong input line:
 _Description: Placement administrator password:
debconf: debian/nova-common.templates.in:77: Wrong input line:
  Please enter the password of the Placement administrator.
debconf: debian/nova-common.templates.in:82: Wrong input line:
 _Description: Placement os region name:
debconf: debian/nova-common.templates.in:83: Wrong input line:
  Please enter the region name for Placement service.
debconf: debian/nova-common.templates.in:88: Wrong input line:
 _Description: Manage neutron config through debconf?
debconf: debian/nova-common.templates.in:89: Wrong input line:
  Nova service must contact Neutron, and this is configured through
debconf: debian/nova-common.templates.in:90: Wrong input line:
  the [neutron] section of the configuration. Specify if you wish
debconf: debian/nova-common.templates.in:91: Wrong input line:
  to handle this configuration through debconf.
debconf: debian/nova-common.templates.in:96: Wrong input line:
 _Description: Manage placement config through debconf?
debconf: debian/nova-common.templates.in:97: Wrong input line:
  Nova service must contact Placement, and this is configured through
debconf: debian/nova-common.templates.in:98: Wrong input line:
  the [placement] section of the configuration. Specify if you wish
debconf: debian/nova-common.templates.in:99: Wrong input line:
  to handle this configuration through debconf.
podebconf: file debian/po/templates.pot not found
podebconf: file debian/po/POTFILES.in not found
debconf: debian/nova-consoleproxy.templates:5: Wrong input line:
 _Description: Type of console daemon to start at boot time:
debconf: debian/nova-consoleproxy.templates:6: Wrong input line:
  Nova Console supports 3 types of consoles. One is specific to Xen, called
debconf: debian/nova-consoleproxy.templates:7: Wrong input line:
  XVP (Xen VNC Proxy), and the other daemon supports KVM. While the SPICE
debconf: debian/nova-consoleproxy.templates:8: Wrong input line:
  protocol is normally faster than VNC, it also requires support for web
debconf: debian/nova-consoleproxy.templates:9: Wrong input line:
  sockets in your browser, and that is a feature only very modern browsers
debconf: debian/nova-consoleproxy.templates:10: Wrong input line:
  have support for.
debconf: debian/nova-consoleproxy.templates:11: Wrong input line:
  .
debconf: debian/nova-consoleproxy.templates:12: Wrong input line:
  This can later be edited in /etc/default/nova-consoleproxy.
podebconf: file debian/po/templates.pot not found
podebconf: file debian/po/POTFILES.in not found
      

Please ask the translator (identified by the Last-Translator field in the PO file), the language team (identified by the Language-Team field) or debian-i18n for a fix.