Bug 997861 - Report presence of the force_clean_build marker for Python...

This is just a minor fix, where if 'force_clean_build' marker exists, print it to console.

Now (devenv_3661) you get this:

```
remote: Stopping PYTHON cart
remote: Waiting for stop to finish
remote: Recreating virtenv
```

With this patch you will get this:

```
remote: .openshift/markers/force_clean_build found!
remote: Recreating virtenv

```