...

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