krb5 commit [krb5-1.17]: In mkrel, build documentation with python3

https://github.com/krb5/krb5/commit/1d8adadb14f732e05b864d178e2068393fd9e777
commit 1d8adadb14f732e05b864d178e2068393fd9e777
Author: Greg Hudson <[email protected]>
Date:   Wed Dec 11 12:09:27 2019 -0500

    In mkrel, build documentation with python3
    
    After commit 95830231758de259abbbccedbac01613f578768a, the
    documentation cannot be built with Python 2.  Run make with
    "PYTHON=python3" to ensure that we use Python 3.
    
    (cherry picked from commit 17b40b1acb8f2e2c1f646ae76a9919089c4ba85c)

 src/util/mkrel |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/util/mkrel b/src/util/mkrel
index d962a64..1bef059 100755
--- a/src/util/mkrel
+++ b/src/util/mkrel
@@ -183,9 +183,9 @@ rm -rf $reldir/.git || true
 if test $dodoc = t; then
 	echo "Building doc..."
 	(cd $reldir/src/doc && make -f Makefile.in \
-	    top_srcdir=.. srcdir=. SPHINX_ARGS=-W PYTHON=python html pdf)
+	    top_srcdir=.. srcdir=. SPHINX_ARGS=-W PYTHON=python3 html pdf)
 	(cd $reldir/src/doc && make -f Makefile.in \
-	    top_srcdir=.. srcdir=. SPHINX_ARGS=-W PYTHON=python clean)
+	    top_srcdir=.. srcdir=. SPHINX_ARGS=-W PYTHON=python3 clean)
 fi
 
 echo "Generating tarfiles..."