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from django.db import DatabaseError


class AmbiguityError(Exception):
    """More than one migration matches a name prefix."""
    pass


class BadMigrationError(Exception):
    """There's a bad migration (unreadable/bad format/etc.)."""
    pass


class CircularDependencyError(Exception):
    """There's an impossible-to-resolve circular dependency."""
    pass


class InconsistentMigrationHistory(Exception):
    """An applied migration has some of its dependencies not applied."""
    pass


class InvalidBasesError(ValueError):
    """A model's base classes can't be resolved."""
    pass


class IrreversibleError(RuntimeError):
    """An irreversible migration is about to be reversed."""
    pass


class NodeNotFoundError(LookupError):
    """An attempt on a node is made that is not available in the graph."""

    def __init__(self, message, node, origin=None):
        self.message = message
        self.origin = origin
        self.node = node

    def __str__(self):
        return self.message

    def __repr__(self):
        return "NodeNotFoundError(%r)" % (self.node,)


class MigrationSchemaMissing(DatabaseError):
    pass


class InvalidMigrationPlan(ValueError):
    pass