Have git-cl try fail when used on a closed CL

R=phajdan.jr@chromium.org, rch@chromium.org

Review URL: https://codereview.chromium.org/494713003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@290844 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -2303,6 +2303,9 @@ def CMDtry(parser, args):
     parser.error('Need to upload first')
 
   props = cl.GetIssueProperties()
+  if props.get('closed'):
+    parser.error('Cannot send tryjobs for a closed CL')
+
   if props.get('private'):
     parser.error('Cannot use trybots with private issue')