Add validation when the input-base-dir is not present

[mcruzdev]

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Fixes #871

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I am not sure if this pull request solves the issue, but I think that shows a better message.

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[ricardozanini]

@fjtirado @hbelmiro mind taking a look?

[hbelmiro]

Thank you @mcruzdev.
Looks good. I just left a few nits.