          Authenticate the userid and password against username and password.
          """
          user = authenticate(username=userid, password=password)
          if user is None or not user.is_active:
              raise exceptions.AuthenticationFailed(_("Invalid username/password."))
          return (user, None)
  
      def authenticate_header(self, request):
          return 'Basic realm="%s"' % self.www_authenticate_realm
  
 
</s> remove             raise exceptions.AuthenticationFailed(_("User inactive or deleted"))
 </s> add             raise exceptions.AuthenticationFailed(_('User inactive or deleted.')) </s> remove             msg = _("Must include \"username\" and \"password\"")
 </s> add             msg = _('Must include "username" and "password".') </s> remove                     msg = _("User account is disabled.")
 </s> add                     msg = _('User account is disabled.') </s> remove     invalid_version_message = _("Invalid version in URL path.")
 </s> add     invalid_version_message = _('Invalid version in URL path.') </s> remove             raise exceptions.AuthenticationFailed(_("Invalid token"))
 </s> add             raise exceptions.AuthenticationFailed(_('Invalid token.'))
            raise exceptions.AuthenticationFailed(_('Invalid username/password.'))
          Authenticate the userid and password against username and password.
          """
          user = authenticate(username=userid, password=password)
          if user is None or not user.is_active:
            raise exceptions.AuthenticationFailed(_('Invalid username/password.'))
          return (user, None)
  
      def authenticate_header(self, request):
          return 'Basic realm="%s"' % self.www_authenticate_realm
  
keep keep keep keep replace keep keep keep keep keep
 prefer single quotes in source and double quotes in user visible strings; add some missing full stops to user visible strings 
rest_framework/authentication.py