  
          try:
              auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
          except (TypeError, UnicodeDecodeError):
              msg = 'Invalid basic header. Credentials not correctly base64 encoded'
              raise exceptions.AuthenticationFailed(msg)
  
          userid, password = auth_parts[0], auth_parts[2]
          return self.authenticate_credentials(userid, password)
  
 
</s> remove             msg = 'Invalid basic header. Credentials string should not contain spaces.'
 </s> add             msg = _("Invalid basic header. Credentials string should not contain spaces.") </s> remove             msg = 'Invalid basic header. No credentials provided.'
 </s> add             msg = _("Invalid basic header. No credentials provided.") </s> remove             msg = 'Invalid token header. Token string should not contain spaces.'
 </s> add             msg = _("Invalid token header. Token string should not contain spaces.") </s> remove             msg = 'Invalid token header. No credentials provided.'
 </s> add             msg = _("Invalid token header. No credentials provided.") </s> remove             raise exceptions.AuthenticationFailed('Invalid token')
 </s> add             raise exceptions.AuthenticationFailed(_("Invalid token"))
            msg = _("Invalid basic header. Credentials not correctly base64 encoded.")
  
          try:
              auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
          except (TypeError, UnicodeDecodeError):
            msg = _("Invalid basic header. Credentials not correctly base64 encoded.")
              raise exceptions.AuthenticationFailed(msg)
  
          userid, password = auth_parts[0], auth_parts[2]
          return self.authenticate_credentials(userid, password)
  
keep keep keep keep replace keep keep keep keep keep
 use double quotes for user visible strings; end user visible strings in full stops; add some missing translation tags 
rest_framework/authentication.py