Upgrade to PHP 7.0

I am attempting to upgrade my site to PHP 7.0 and I first ran the php-compatibility checker. I am on WordPress 4.9.6 and wp-cassify 2.1.4.

I receive 2 errors from the wp-cassify plugin…any ideas for how to fix?

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FILE: /<site info>/plugins/wp-cassify/classes/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/SimpleMailInvoker.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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33 | WARNING | INI directive ‘safe_mode’ is deprecated since PHP 5.3 and removed since PHP 5.4
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FILE: /<site info>/wp-content/plugins/wp-cassify/classes/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/Esmtp/Auth/NTLMAuthenticator.php
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FOUND 1 ERROR AFFECTING 1 LINE
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528 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0