[recipe_modules/file] add real file module to engine.

recipe_engine/unittests/run_test.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 import json
 import os
 import re
 import subprocess
 import unittest
@@ skipping 43 matching lines @@
         0, proc.returncode, recipe, stdout))
 
   def test_examples(self):
     tests = [
       ['step:examples/full'],
       ['path:examples/full'],
       ['raw_io:examples/full'],
       ['python:examples/full'],
       ['json:examples/full'],
       ['uuid:examples/full'],
+      ['file:examples/copy'],
+      ['file:examples/copytree'],
 
       ['engine_tests/depend_on/top', {'to_pass': 42}],
       ['engine_tests/functools_partial'],
     ]
     for test in tests:
       self._test_recipe(*test)
 
   def test_bad_subprocess(self):
     now = time.time()
     self._test_recipe('engine_tests/bad_subprocess')
@@ skipping 184 matching lines @@
             u'foo',
             u'bar',
             u'baz',
           ],
         })
 
 
 if __name__ == '__main__':
   unittest.TestCase.maxDiff = None
   unittest.main()