be more specific

Signed-off-by: Kenneth Reitz <me@kennethreitz.org>

bin/steps/python

@@ -7,13 +7,13 @@ PYTHON_VERSION=$(cat runtime.txt)
 if [[ $PYTHON_VERSION =~ ^python-2 ]]; then
   if [[ "$PYTHON_VERSION" != "$LATEST_2" ]]; then
     puts-warn "The latest version of Python 2 is $LATEST_2 (you are using $PYTHON_VERSION, which is unsupported)."
-    puts-warn "We recommend upgrading by specifying the latest version."
+    puts-warn "We recommend upgrading by specifying the latest version ($LATEST_2)."
     echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
   fi
 else
   if [[ "$PYTHON_VERSION" != "$LATEST_3" ]]; then
     puts-warn "The latest version of Python 3 is $LATEST_3 (you are using $PYTHON_VERSION, which is unsupported)."
-    puts-warn "We recommend upgrading by specifying the latest version."
+    puts-warn "We recommend upgrading by specifying the latest version ($LATEST_3)."
     echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
   fi