Fixes a fatal bug when the module has computed alternatives containing %s.
diff --git a/Lib/webbrowser.py b/Lib/webbrowser.py
index ebafd80..d882e7f 100644
--- a/Lib/webbrowser.py
+++ b/Lib/webbrowser.py
@@ -24,7 +24,7 @@
     for browser in alternatives:
         if browser.find('%s') > -1:
             # User gave us a command line, don't mess with it.
-            return browser
+            return GenericBrowser(browser)
         else:
             # User gave us a browser name.
             command = _browsers[browser.lower()]