Comment 1 for bug 1216412

error and note were deprecated in 2.1.0 and removed from trace.py in the 2.4 cycle.

At that point the their code was:

@deprecated_function(deprecated_in((2, 1, 0)))
def info(*args, **kwargs):
    """Deprecated: use trace.note instead."""
    note(*args, **kwargs)

@deprecated_function(deprecated_in((2, 1, 0)))
def log_error(*args, **kwargs):
    """Deprecated: use bzrlib.trace.show_error instead"""
    _bzr_logger.error(*args, **kwargs)

@deprecated_function(deprecated_in((2, 1, 0)))
def error(*args, **kwargs):
    """Deprecated: use bzrlib.trace.show_error instead"""
    _bzr_logger.error(*args, **kwargs)

So the plugin needs to be updated.