Don't include traceback when wrapping exceptions
Don't include traceback when wrapping exceptions

The fix in fa52cb09b2270876c9d9a03106f961be6c9db834 strips tracebacks
from exceptions when returning them to the user, but it still spams
the log with a long traceback. We shouldn't be including the traceback
when we wrap the exception in the first place. Instead we just
include the message.

It also updates the error code to 409 for device in use since this
is actually a conflict.

Fix for:

  bug 1155315
  bug 1103324
  bug 1092610

Change-Id: I95019a3022eb52e0335c455009c13fe229475d03

n0ano/gantt,n0ano/gantt