Also handle IOError in roll_dep.py.

TBR=smut@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1150413002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295391 0039d316-1c4b-4281-b951-d872f2087c98

roll_dep.py

@@ -28,7 +28,7 @@ def roll(root, deps_dir, key, reviewers, bug):
   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