temporary workaround for libguestfs bug (BZ 790528)

imagefactory

@@ -20,6 +20,7 @@ import os
 import os.path
 import signal
 import logging
+import guestfs
 from imgfac.ApplicationConfiguration import ApplicationConfiguration
 from imgfac.BuildDispatcher import BuildDispatcher
 from imgfac.Singleton import Singleton
@@ -140,6 +141,8 @@ class Application(Singleton):
 
             debug(self.app_config['debug'])
             pem_file = self.app_config['ssl_pem'] if not self.app_config['no_ssl'] else None
+            # TODO: Remove this call and the function def when BZ 790528 is resolved
+            self._init_guestfs()
             # Don't set reloader to True or you will lose state.  You have been warned.
             run(server='paste',
                     app=rest_api,
@@ -182,5 +185,12 @@ class Application(Singleton):
                 for dispatcher in dispatchers:
                     print("Pushing build %s of image %s to provider %s" % (dispatcher.build_id, dispatcher.image_id, dispatcher.provider))
 
+    def _init_guestfs(self):
+        # Doing this once, before going multithreaded, avoids the concurrency issue in BZ 790528
+        g = guestfs.GuestFS()
+        g.add_drive ("/dev/zero")
+        g.launch()
+        del g
+
 if __name__ == "__main__":
     sys.exit(Application().main())