for google translate, error if destination language is 'auto'.

plugins/Google/plugin.py

@@ -268,6 +268,9 @@ class Google(callbacks.PluginRegexp):
             toLang = lang.normalize('lang_'+toLang)[5:]
         if fromLang == 'auto':
             fromLang = ''
+        if toLang == 'auto':
+            irc.error("Destination language cannot be 'auto'.")
+            return
         opts['langpair'] = '%s|%s' % (fromLang, toLang)
         fd = utils.web.getUrlFd('%s?%s' % (self._gtranslateUrl,
                                            urllib.urlencode(opts)),

plugins/Google/test.py

@@ -60,6 +60,7 @@ class GoogleTestCase(ChannelPluginTestCase):
         def testTranslate(self):
             self.assertRegexp('translate en es hello world', 'mundo')
             self.assertRegexp('translate auto en ciao', 'Italian.*hello')
+            self.assertError('translate en to auto stuff')
 
         def testCalcDoesNotHaveExtraSpaces(self):
             self.assertNotRegexp('google calc 1000^2', r'\s+,\s+')