checked in virtualenv safety check

bin/compile

@@ -33,6 +33,12 @@ if [ "$NAME" = "Python" ]; then
   [ -f manage.py ] && [ -f settings.py ] && { echo " !     Django app must be in a package subdirectory"; exit 1; }
 fi
 
+# reject a checked-in virtualenv
+if [ -d "lib" ] || [ -d "bin" ]; then
+  echo " !     You have a virtualenv checked in. You should ignore the appropriate paths in your repo. See http://devcenter.heroku.com/articles/gitignore for more info.";
+  exit 1;
+fi
+
 # copy artifacts out of cache if exists
 mkdir -p $CACHE_DIR
 for dir in $VIRTUALENV_DIRS; do