Also handle IOError in roll_dep.py.

roll_dep.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Rolls DEPS controlled dependency.
 
 Works only with git checkout and git dependencies.
 """
 
@@ skipping 10 matching lines @@
   return not (
       subprocess.check_output(cmd, cwd=root).strip() or
       subprocess.check_output(cmd + ['--cached'], cwd=root).strip())
 
 
 def roll(root, deps_dir, key, reviewers, bug):
   deps = os.path.join(root, 'DEPS')
   try:
     with open(deps, 'rb') as f:
       deps_content = f.read()
-  except OSError:
+  except (IOError, OSError):
     print >> sys.stderr, (
         'Ensure the script is run in the directory containing DEPS file.')
     return 1
 
   if not is_pristine(root):
     print >> sys.stderr, 'Ensure %s is clean first.' % root
     return 1
 
   full_dir = os.path.join(os.path.dirname(root), deps_dir)
   head = subprocess.check_output(
@@ skipping 88 matching lines @@
   return roll(
       os.getcwd(),
       args[0],
       args[1] if len(args) > 1 else None,
       reviewers,
       options.bug)
 
 
 if __name__ == '__main__':
   sys.exit(main())