At the moment it just fetches the patch. It's still useful to debug rietveld
issues.

Improve resiliency to invalid patches.

R=dpranke@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/6825085

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@81305 0039d316-1c4b-4281-b951-d872f2087c98