view mercurial/thirdparty/attr/exceptions.py @ 46779:49fd21f32695

revlog: guarantee that p1 != null if a non-null parent exists

This change does not affect the hashing (which already did this
transformation), but can change the log output in the rare case where
this behavior was observed in repositories. The change can simplify
iteration code where regular changesets and merges are distinct
branches.

Differential Revision: https://phab.mercurial-scm.org/D10150

from __future__ import absolute_import, division, print_function


class FrozenInstanceError(AttributeError):
    """
    A frozen/immutable instance has been attempted to be modified.

    It mirrors the behavior of ``namedtuples`` by using the same error message
    and subclassing :exc:`AttributeError`.

    .. versionadded:: 16.1.0
    """
    msg = "can't set attribute"
    args = [msg]


class AttrsAttributeNotFoundError(ValueError):
    """
    An ``attrs`` function couldn't find an attribute that the user asked for.

    .. versionadded:: 16.2.0
    """


class NotAnAttrsClassError(ValueError):
    """
    A non-``attrs`` class has been passed into an ``attrs`` function.

    .. versionadded:: 16.2.0
    """


class DefaultAlreadySetError(RuntimeError):
    """
    A default has been set using ``attr.ib()`` and is attempted to be reset
    using the decorator.

    .. versionadded:: 17.1.0
    """