Enable plugins so that we can use the priorities plugin

This might not be the best idea - e.g. just because you enable
and configure a plugin doesn't mean you want to change the
behaviour of pungi.

Possible alternatives:

 - add some way to make yum load a specific plugin with a
   specific configuration
 - add the code for handling repo priorities into pungi
 - add the code for handling repo priorities into yum itself

Note, it would most likely make sense for e.g. anaconda and
livecd-creator to also handle priorities, so this isn't just
and issue for pungi

Signed-off-by: Mark McLoughlin <markmc@redhat.com>

Index: pungi/pypungi/gather.py
===================================================================
--- pungi.orig/pypungi/gather.py
+++ pungi/pypungi/gather.py
@@ -81,6 +81,9 @@ class Gather(vpro.pypungi.PungiBase):
         yumvars['basearch'] = yum.rpmUtils.arch.getBaseArch(myarch=self.config.get('default', 'arch'))
         yumconf.yumvar = yumvars
         self.ayum._conf = yumconf
+        self.ayum.doPluginSetup(plugin_types = (yum.plugins.TYPE_CORE, ),
+                                searchpath = yum.config.StartupConf.pluginpath.default,
+                                confpath = yum.config.StartupConf.pluginconfpath.default)
         self.ayum.repos.setCacheDir(self.ayum.conf.cachedir)
 
         self.ayum.cleanMetadata() # clean metadata that might be in the cache from previous runs

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