* Fix test failure when GPG raises ``InvalidSigners`` instead of
``GPGMEError`` on systems without usable secret keys.
* Object store ``close()`` methods can now be called multiple times safely.
Object stores now raise ``ResourceWarning`` when destroyed with unclosed
resources.
OBS-URL: https://build.opensuse.org/package/show/devel:tools:scm/python-dulwich?expand=0&rev=41
