[Review] Request from 'tgoettlicher' @ 'SUSE/machinery/review_140805_'

Please review the following changes:
  * c70891a Show installation instructions for glance client on SLE12 if not installed
  * 6425d43 Merge branch 'fix-exception'
  * 5f42e71 Use correct exception
not sure about it but such error messages are great when machinery runs on SLES12 but on any other distribution it would be misleading. That's because

- modules exists on SLE12 only
- yast exists for SUSE only
- zypper exists for SUSE only
- The term package is handled differently on many distributions, rpm, deb

Now that machinery is an opensource project and imho not only targeted to SUSE respectively SLES we should not create such distro specific error messages. I would rather print something globally correct like

```
required software/subsystem/tool/program was not found, read chapter X in the machinery documentation for details
```

and then have documentation which explains what needs to be done on openSUSE, on SLES on wherever else

don't treat this comment as blocking the solution here, all is fine and I don't have any merge objections. I just though I should have written down my thoughts here.