py-gssapi: Add kerberos5 variant, to allow use of MIT Kerberos

python/py-gssapi/Portfile

@@ -22,7 +22,28 @@ checksums           rmd160  71966a7d6bf97fca5ccf27f687334b53f8bd1d85 \
 
 python.versions     39 310 311 312 313
 
-patchfiles          patch-setup.py.diff
+# python-gssapi knows when it's running on macOS, and automatically configures
+# itself to use macOS' GSSAPI Framework, which uses macOS' build of Heimdal
+# Kerberos.
+variant kerberos5 description {Use MIT Kerberos} {
+    long_description-append  Uses GSSAPI/Kerberos from MacPorts' kerberos5 \
+                             package.
+    depends_lib-append       port:kerberos5
+
+    # Support for MIT Kerberos has been brought up upstream before, in
+    # https://github.com/pythongssapi/python-gssapi/issues/347
+    # In that GitHub issue, this is how the devs say to use MIT Kerberos.
+    pre-build {
+        set gssapi_cflags    [exec ${prefix}/bin/krb5-config --cflags gssapi]
+        set gssapi_libs      [exec ${prefix}/bin/krb5-config --libs gssapi]
+        build.env-append     GSSAPI_MAIN_LIB=${prefix}/lib/libgssapi_krb5.dylib \
+                             GSSAPI_COMPILER_ARGS=${gssapi_cflags} \
+                             GSSAPI_LINKER_ARGS=${gssapi_libs}
+    }
+}
+if {![variant_isset kerberos5]} {
+    long_description-append  Uses macOS's built-in GSSAPI/Kerberos.
+}
 
 if {${name} ne ${subport}} {
     depends_build-append    port:py${python.version}-setuptools \
@@ -34,7 +55,11 @@ if {${name} ne ${subport}} {
 
     # Uses GSS.framework on macOS >= 10.9
     if {${os.platform} eq "darwin" && ${os.major} < 13} {
-        depends_lib-append  port:kerberos5
+        default_variants    +kerberos5
+        if {![variant_isset kerberos5]} {
+            ui_error "Built-in GSSAPI/Kerberos is not usable on Mac OS X below 10.9."
+            return -code error
+        }
     }
 
     livecheck.type          none