Pecan's debug mode can be terribly insecure; 500 errors return a
Python traceback, the full list of environment variables, and a
button to replay the request with a breakpoint.
Deployers often run OpenStack services in debug mode; doing so should
not open the service up to these flaws. However, it may be useful
to use Pecan's debug mode in development, so create a config option
to enable it, rather than disable it altogether.
Change-Id: I5bc76b4101c563cdc168d2e55db060c1bdd0b5fe
Closes-Bug: #1425206
0f4d454bf2