Raise dedicated exception for LOCK_ACQUISITION_FAIL

[jarus]

If an application uses SQLAlchemy-HANA for serialized transaction updates with SELECT ... FOR UPDATE then you probably find something like the following in various places:

try:
    # SELECT ... WITH FOR UPDATE NOWAIT
except DBAPIError as exc:
    if exc.orig.errorcode == 146:
        # Special handling

A better and more reusable approach could be the introduction of a dedicated SQLAlchemy-HANA exception like RowLockAcquisitionError.