[file] fix glob_paths when NO paths match, add tests.

recipe_modules/file/resources/fileutil.py

 #!/usr/bin/env python
 # Copyright 2017 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.
 
 """Utility exporting basic filesystem operations.
 
 This file was cut from "scripts/common/chromium_utils.py" at:
 91310531c31fa645256b4fb5d44b460c42b3e151
 """
@@ skipping 136 matching lines @@
   if not os.path.isdir(dest):
     if os.path.exists(dest):
       raise OSError(errno.EEXIST, os.strerror(errno.EEXIST))
     os.makedirs(dest, mode)
 
 
 def _Glob(base, pattern):
   cwd = os.getcwd()
   try:
     os.chdir(base)
-    print('\n'.join(sorted(glob.glob(pattern))))
+    hits = glob.glob(pattern)
+    if hits:
+      print('\n'.join(sorted(hits)))
   finally:
     os.chdir(cwd)
 
 
 def _Remove(path):
   try:
     os.remove(path)
   except OSError as e:
     if e.errno != errno.ENOENT:
       raise
@@ skipping 101 matching lines @@
     data['message'] = 'UNKNOWN: %s' % e
 
   with opts.json_output:
     json.dump(data, opts.json_output)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))