KeyError: 'releases' for pypi backend

[Zlopez]

The unyanked versions from pypi introduced a new error:

[2022-06-20 17:22:36,608 anitya ERROR] 'releases'
Traceback (most recent call last):
  File "/usr/local/bin/check_service.py", line 223, in run
    future.result()
  File "/usr/lib64/python3.10/concurrent/futures/_base.py", line 439, in result
    return self.__get_result()
  File "/usr/lib64/python3.10/concurrent/futures/_base.py", line 391, in __get_result
    raise self._exception
  File "/usr/lib64/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/bin/check_service.py", line 106, in update_project
    utilities.check_project_release(project, session)
  File "/usr/local/lib/python3.10/site-packages/anitya/lib/utilities.py", line 86, in check_project_release
    versions_prefix = backend.get_versions(project)
  File "/usr/local/lib/python3.10/site-packages/anitya/lib/backends/pypi.py", line 109, in get_versions
    for version in data["releases"]:
KeyError: 'releases'