lib/_yaml/__init__.py

# This is a stub package designed to roughly emulate the _yaml
# extension module, which previously existed as a standalone module
# and has been moved into the `yaml` package namespace.
# It does not perfectly mimic its old counterpart, but should get
# close enough for anyone who's relying on it even when they shouldn't.
import yaml

if not yaml.__with_libyaml__:
    from sys import version_info

    exc = ModuleNotFoundError if version_info >= (3, 6) else ImportError
    raise exc("No module named '_yaml'")
else:
    from yaml._yaml import *
    import warnings
    warnings.warn(
        'The _yaml extension module is now located at yaml._yaml'
        ' and its location is subject to change.  To use the'
        ' LibYAML-based parser and emitter, import from `yaml`:'
        ' `from yaml import CLoader as Loader, CDumper as Dumper`.',
        DeprecationWarning
    )
    del warnings
    # Don't `del yaml` here because yaml is actually an existing
    # namespace member of _yaml.

__name__ = '_yaml'
# If the module is top-level (i.e. not a part of any specific package)
# then the attribute should be set to ''.
# https://docs.python.org/3.8/library/types.html
__package__ = ''