Czech birth number validation issue

[Stranger6667]

As stated in the source code (here)

Three digits for verification number were used until 1. january 1954

And then there is the following condition check:

    if len(id) == 3:
        return '%s' % value

This means, that birth numbers that were issued after 1954.1.1 but don't have fourth digit in it will not be validated. But in fact they are invalid. For example:

Birth number: 600110/0006

This one passes the validation, but if I remove the last digit it will still pass the validation, but it should not because it has to have control digit.

PR: #316