fixes #7445 and BZ1139894 - optionally utilize the RHSCL

This will optionally create a local repo if the ISO contains
the RHSCL repository.  This allows users to install without
a remote RHSCL repository
Can you change the above section to something like

```python
"""
[scl-local]
name=scl-local
baseurl=file://%(baseurl)s/RHSCL
enabled=1
gpgcheck=%(gpgcheck)s""" % dict (baseurl = DEST_DIR, gpgcheck = GPG_CHECK))
```