[Plugins] Allow enabling any plugin Python version

Users encounter issues when trying to install plugins with differing
python versions. If the plugin was built with Py2.6 but they are using
Py2.7 the plugin would not load. With the move to Python 3 this could
become more of an issue. The workaround is to let the plugin manager
to try to load the deluge plugin regardless of the python version it
was built with.

This will put the onus on plugin author to keep the plugin code
compatible with more Python versions.

deluge/pluginmanagerbase.py

@@ -106,7 +106,7 @@ class PluginManagerBase(object):
         pkg_resources.working_set.add_entry(user_plugin_dir)
         plugins_dirs.append(user_plugin_dir)
 
-        self.pkg_env = pkg_resources.Environment(plugins_dirs)
+        self.pkg_env = pkg_resources.Environment(plugins_dirs, None)
 
         self.available_plugins = []
         for name in self.pkg_env: