Turn IPA scripts to python3 -bb for testing
    
    This is a commit which expands current scripts being run under
    python3 by default. We set the -bb option so that any Bytes/Str
    error breaks execution.
    
    This commit shall be reverted before reaching production.
    
    https://pagure.io/freeipa/issue/4985
    
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>