Alexander Reelsen b465e19e5f Release script: Always check for valid environment
In order to be sure that a release can be executed on the local machine,
the build_release script now checks for environment variables and tries
to execute a  couple of commands.

In order to easily check for a correctly setup environment, you can
run the following commands, which exits early and does not trigger a
release process.

```
python3 dev-tools/build_release.py --check-only
```
2015-05-26 14:43:29 +02:00
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