Before, the code might fail due to Errno::ENOTEMPTY and Errno::ENOENT,
possibly caused by time-of-check-to-time-of-use issues, like:

  Schleuder::Filters.key_auto_import_from_attachments imports key and reports new key
  Failure/Error: FileUtils.remove_entry(ENV['GNUPGHOME'])
  Errno::ENOENT:
    No such file or directory @ apply2files - /tmp/d20250105-2974-yvugch/S.gpg-agent.ssh
  # ./lib/schleuder/gpgme/key_extractor.rb:26:in `extract_by_email_address'
  # ./lib/schleuder/email_key_importer.rb:26:in `filter_and_maybe_import_keys'
  # ./lib/schleuder/email_key_importer.rb:9:in `block in import_from_attachments'
  # ./lib/schleuder/email_key_importer.rb:7:in `map'
  # ./lib/schleuder/email_key_importer.rb:7:in `import_from_attachments'
  # ./lib/schleuder/filters/post_decryption/35_key_auto_import_from_attachments.rb:7:in `key_auto_import_from_attachments'
  # ./spec/schleuder/unit/filters_spec.rb:394:in `block (3 levels) in <top (required)>'
  # ./spec/spec_helper.rb:60:in `block (3 levels) in <top (required)>'
  # /usr/local/bundle/gems/database_cleaner-core-2.0.1/lib/database_cleaner/strategy.rb:30:in `cleaning'
  # /usr/local/bundle/gems/database_cleaner-core-2.0.1/lib/database_cleaner/cleaners.rb:34:in `block (2 levels) in cleaning'
  # /usr/local/bundle/gems/database_cleaner-core-2.0.1/lib/database_cleaner/cleaners.rb:35:in `cleaning'
  # ./spec/spec_helper.rb:59:in `block (2 levels) in <top (required)>'