cython: Add error codes and messages for LOCKDOWN_E_PAIRING_DIALOG_PENDING and LOCKDOWN_E_USER_DENIED_PAIRING

Change-Id: I159fe465ee964c391c130b756404fb80f56e160a
cython: Don't fail printing an error message with no string description

Change-Id: I571e5f01423b505223ef7a9b1faedcb94011acd3