Generate message when raising

include/sardine.py

@@ -80,7 +80,7 @@ class Subcommand(object):
                 module = imp.load_module(self.name, fh, modpath,
                                          (".py", "r", imp.PY_SOURCE))
         except IOError:
-            raise SardinePluginError(self.name)
+            raise SardinePluginError("no such plugin: %s" % self.name)
         self.plugin = module.Plugin(self.plugindata)
 
     def _format_output(self, raw):
@@ -103,7 +103,7 @@ class App:
         try:
             self.subcommand = Subcommand(cmdargs, self.pluginpath)
         except SardinePluginError as e:
-            self.die("no such plugin: %s" % e)
+            self.die(e)
 
     def _set_pluginpath(self):
         mypath = os.path.dirname(os.path.realpath(sys.argv[0]))