Ensure __toString() catches all error types

[tylers-username]

Description (*)

In PHP 7.1 catch (\Exception ...) does not catch fatal errors. Because this function can possibly throw fatal errors such as "Call to a member function getRequestFieldName() on null" which is an instance of \Error, we should catch \Throwable to ensure the exception makes it into the logger and $result is assigned the message.

Fixed Issues (if relevant)

1. Exception message expected to be assigned to a variable is instead handled by PHP's default Fatal Error handler.

Contribution checklist (*)

• [*] Pull request has a meaningful description of its purpose
• [*] All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• [*] All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @tylerssn. Thank you for your contribution
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[magento-engcom-team]

Hi @rogyar, thank you for the review.
ENGCOM-4423 has been created to process this Pull Request

[magento-engcom-team]

@tylerssn thank you for contributing. Please accept Community Contributors team invitation here to gain extended permissions for this repository.

[tylers-username]

Done, @magento-engcom-team. Thank you.

[soleksii]

✔️ QA Passed

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