Print content of description backup on exit

R=apolito@google.com

Bug: 1056193
Change-Id: I656149b8ddad61f6b673193b72d780b72a585f43
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2078308
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Anthony Polito <apolito@google.com>

git_cl.py

@@ -133,6 +133,10 @@ _IS_BEING_TESTED = False
 def DieWithError(message, change_desc=None):
   if change_desc:
     SaveDescriptionBackup(change_desc)
+    print('\n ** Content of CL description **\n' +
+          '='*72 +  '\n' +
+          change_desc + '\n' +
+          '='*72 + '\n')
 
   print(message, file=sys.stderr)
   sys.exit(1)