Abstract shell calls, add shlex

[bschroeter]

It would be good to have a single point to test with automatic shell command escaping.

The logic here is to have a single interface to communicate with the shell, rather that recreating the subprocess object each time.

The function would take a command with arguments, automatically shell-escaping the arguments with shlex (protecting from shell injection). Any additional kwargs will be passed directly to subprocess to override the default arguments.

This could be a common function somewhere?

[SeanBryan51]

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