The VolunteerReport class gives an error: "Unknown extension key in a translation string: org.civicrm.volunteer."
Reproduceable in CiviCRM 4.7.19 install with CiviVolunteer master.
Steps to reproduce:
- In "Administer / Localization / Languages, Currency, Locations", Ensure default language is set to something other than "English (United States)"
- Go to "Reports / Contact Reports" and load the "Volunteer Report"
- Error message is displayed