TypeError: load() missing 1 required positional argument: 'Loader'

Bad ending while trying to build duplicity snap on GitLab.

Sorry, an error occurred in Snapcraft:
We would appreciate it if you created a bug report at
https://launchpad.net/snapcraft/+filebug with the above text included.
Traceback (most recent call last):
  File "/usr/bin/snapcraft", line 11, in <module>
    load_entry_point('snapcraft==2.43.1+18.4.1', 'console_scripts', 'snapcraft')()
  File "/usr/lib/python3/dist-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/lifecycle.py", line 136, in snap
    project = _execute(steps.PRIME, parts=[], **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/lifecycle.py", line 35, in _execute
    lifecycle.execute(step, project_config, parts)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 90, in execute
    executor.run(step, part_names)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 196, in run
    self._create_meta(step, processed_part_names)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 354, in _create_meta
    common.env = self.config.snap_env()
  File "/usr/lib/python3/dist-packages/snapcraft/internal/project_loader/_config.py", line 289, in snap_env
    dependency_paths |= part.get_primed_dependency_paths()
  File "/usr/lib/python3/dist-packages/snapcraft/internal/pluginhandler/__init__.py", line 885, in get_primed_dependency_paths
    state = self.get_prime_state()
  File "/usr/lib/python3/dist-packages/snapcraft/internal/pluginhandler/__init__.py", line 144, in get_prime_state
    self._prime_state = cast(states.PrimeState, self.get_state(steps.PRIME))
  File "/usr/lib/python3/dist-packages/snapcraft/internal/pluginhandler/__init__.py", line 148, in get_state
    return states.get_state(self.plugin.statedir, step)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/states/_state.py", line 96, in get_state
    state = yaml.load(f.read())
TypeError: load() missing 1 required positional argument: 'Loader'