Add missing argument to os.environ

Fixes #1264

powerline/bindings/config.py

@@ -90,7 +90,7 @@ class EmptyArgs(object):
 def init_environment(pl, args):
 	'''Initialize tmux environment from tmux configuration
 	'''
-	powerline = ShellPowerline(finish_args(EmptyArgs('tmux', args.config_path)))
+	powerline = ShellPowerline(finish_args(os.environ, EmptyArgs('tmux', args.config_path)))
 	# TODO Move configuration files loading out of Powerline object and use it 
 	# directly
 	powerline.update_renderer()