remove purging of old virtualenvs

 since old stacks aren't supported

bin/compile

@@ -27,10 +27,6 @@ BUILD_DIR=$1
 CACHE_DIR=$2
 ENV_DIR=$3
 
-# Static configurations for virtualenv caches.
-VIRTUALENV_LOC=".heroku/venv"
-LEGACY_TRIGGER="lib/python2.7"
-
 DEFAULT_PYTHON_VERSION="python-2.7.13"
 DEFAULT_PYTHON_STACK="cedar-14"
 PYTHON_EXE="/app/.heroku/python/bin/python"
@@ -133,12 +129,6 @@ fi
 # Prepare the cache.
 mkdir -p $CACHE_DIR
 
-# Purge "old-style" virtualenvs.
-bpwatch start clear_old_venvs
-  [ -d $CACHE_DIR/$LEGACY_TRIGGER ] && rm -fr $CACHE_DIR/.heroku/bin $CACHE_DIR/.heroku/lib $CACHE_DIR/.heroku/include
-  [ -d $CACHE_DIR/$VIRTUALENV_LOC ] && rm -fr $CACHE_DIR/.heroku/venv $CACHE_DIR/.heroku/src
-bpwatch stop clear_old_venvs
-
 # Restore old artifacts from the cache.
 bpwatch start restore_cache
     mkdir -p .heroku