Merge pull request heroku#47 from ojno/master

Option to purge and recreate virtualenv

Author: Kenneth Reitz

bin/compile

@@ -160,12 +160,14 @@ puts-step "Creating Virtualenv version $(virtualenv --version)"
 # Try to create the virtualenv.
 OUT=$(virtualenv --python $PYTHON_EXE --distribute --never-download --prompt='(venv) ' $VIRTUALENV_LOC 2>&1)
 
-# If there's an error, purge and recreate.
-[ $? -ne 0 ] && {
-  puts-warn "Virtualenv corrupt, rebuilding."
+[ $? -ne 0 -o -n "$CLEAN_VIRTUALENV" ] && {
+  if [ -n "$CLEAN_VIRTUALENV" ]
+    then echo " !     CLEAN_VIRTUALENV set, rebuilding virtualenv."
+    else echo " !     Virtualenv corrupt, rebuilding."
+  fi
   for dir in $VIRTUALENV_DIRS; do
     rm -fr $dir &> /dev/null || true
-  done
+  done  
   OUT=$(virtualenv --python $PYTHON_EXE --distribute --never-download  --prompt='(venv) ' $VIRTUALENV_LOC )
 }
 echo "$OUT" | indent
@@ -222,4 +224,4 @@ done
 # Experimental post_compile hook.
 source $BIN_DIR/steps/hooks/post_compile
 
-# <a href="http://github.com/heroku/heroku-buildpack-python"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://d3nwyuy0nl342s.cloudfront.net/img/7afbc8b248c68eb468279e8c17986ad46549fb71/687474703a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f6461726b626c75655f3132313632312e706e67" alt="Fork me on GitHub"></a>
+# <a href="http://github.com/heroku/heroku-buildpack-python"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://d3nwyuy0nl342s.cloudfront.net/img/7afbc8b248c68eb468279e8c17986ad46549fb71/687474703a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f6461726b626c75655f3132313632312e706e67" alt="Fork me on GitHub"></a>