python/cryptography: Add python3 support.

Signed-off-by: Andrew Clemons <andrew.clemons@gmail.com>
Signed-off-by: Willy Sudiarto Raharjo <willysr@slackbuilds.org>

python/cryptography/cryptography.SlackBuild

@@ -73,6 +73,11 @@ find -L . \
 
 python setup.py install --root=$PKG
 
+# Python 3 support.
+if $(python3 -c 'import sys' 2>/dev/null); then
+  python3 setup.py install --root=$PKG
+fi
+
 find $PKG -print0 | xargs -0 file | grep -e "executable" -e "shared object" | grep ELF \
   | cut -f 1 -d : | xargs strip --strip-unneeded 2> /dev/null || true