[recipes.py] move run arg parsing to its module.

recipe_engine/depgraph.py

 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 from __future__ import print_function
 
-import argparse
 import sys
 
 from . import loader
 
+from . import env
+
+import argparse  # this is vendored
+
 
 _GRAPH_HEADER = """strict digraph {
   concentrate = true;
   ranksep = 2;
   nodesep = 0.25;
 """
 
 _GRAPH_FOOTER = """}
 """
 
@@ skipping 114 matching lines @@
     print('  subgraph "cluster_%s" { label="%s"; %s; }' % (
         package, package, '; '.join(modules)), file=args.output)
 
   if args.recipe_filter and recipe_to_package:
     recipe_names = [
         '"recipe %s"' % name for name in recipe_to_package.keys()]
     print('  subgraph "cluster_recipes" { label="recipes"; %s; }' % (
         '; '.join(recipe_names)), file=args.output)
 
   print(_GRAPH_FOOTER, file=args.output)