Support for running tests against Heimdal in CI

[jborean93]

This requires pythongssapi/k5test#13 to be reviewed/merged/released first as currently it is installing straight from source to verify the tests do in fact work. Once that is done the lines https://github.com/pythongssapi/python-gssapi/pull/262/files#diff-0466ec3bdb3913aba71d897f97c298a0de3f922e14fe75af374e16e8478104c3R111-R114 can be removed from this PR.

I initially looked at running these tests on Windows as well but it doesn't look like MIT Kerberos on Windows provides a kdc service so I dropped that idea.

Should fix #233 - at least combined with the k5test PR.

[frozencemetery]

There are several "if not heimdal" or "if not darwin" checks - are you intentionally assuming that macOS implies distro heimdal? It's tricky because I think there are three different GSSAPIs one could be using on macOS. I also don't know whether this is worth caring about.

Additional thoughts inline.

[jborean93]

are you intentionally assuming that macOS implies distro heimdal?

Somewhat, as you have said someone could have MIT Kerberos, GSS.framework Heimdal, or pure Heimdal installed on macOS so there's no easy way to detect this. I could reuse GSSAPI_KRB5_MAIN_LIB as the check for GSS.framework Heimdal on macOS but at this point it seemed overkill for a very niche scenario. It would also mean that tests will fail on someone who is running with GSS.framework by default as now they would need to set that env var to something that is expected. IMO I think the chances of someone running tests on macOS and they are not using GSS.framework are quite low and not worth considering until someone does encounter it.

Additional thoughts inline.

Thanks, the changes have been made.

[frozencemetery]

Thanks!