fix error message

isso/dispatch.py

@@ -2,7 +2,6 @@
 
 import sys
 import os
-import os.path
 import logging
 
 from glob import glob
@@ -47,19 +46,19 @@ class Dispatcher(DispatcherMiddleware):
         resp = Response("\n".join(self.isso.keys()), 404, content_type="text/plain")
         return resp(environ, start_response)
 
-settings = os.environ.get("ISSO_SETTINGS")
 
+settings = os.environ.get("ISSO_SETTINGS")
 if settings:
     if os.path.isdir(settings):
-        conf_glob = os.path.join(os.environ["ISSO_SETTINGS"], '*.cfg')
+        conf_glob = os.path.join(settings, '*.cfg')
         confs = glob(conf_glob)
         application = wsgi.SubURI(Dispatcher(*confs))
     else:
-        confs = os.environ["ISSO_SETTINGS"].split(";")
+        confs = settings.split(";")
         for path in confs:
             if not os.path.isfile(path):
                 logger.fatal("%s: no such file", path)
                 sys.exit(1)
     application = wsgi.SubURI(Dispatcher(*confs))
 else:
-    logger.fatal('environment variable ISSO_SETTINGS or ISSO_SETTINGS_DIR must be set')
+    logger.fatal('environment variable ISSO_SETTINGS must be set')