Check environment

[tomschr]

Situation

In the past, we had problems about having not enough space. Or commands not being found. Or the wrong version.

Use Case

Before you start the doc build, check the environment. It helps to avoid situations where you run the command, but the command is missing, has the wrong version, or the disc run out of space.

We don't want to have these failures in the middle of a build.

Possible Implementation

We check before we run:

• Check if the required commands (daps, jing, xmllint, rsync, ...) are available in the PATH.
• Check if the commands need to fullfil a minimum version.
• Check if the free space on the disk is enough. We could check space on the target path, on /var/, or on other paths. The paths need to be retrieved from the config file.
• Check if the paths defined in the env config(s) are a) available and b) the current user can write into this directory.

Relation

See #21