Replaced exception with messageManager error message due to user error and not application error

[woutersamaey]

Replaced exception with messageManager error message due to user error and not application error

Description (*)

When subscribing to the newsletter with an existing email address, an exception is thrown, then later caught, added as error message + logged. Since this is a user error, it should not be logged. Our log files don't need these kinds of messages.

Fixed Issues (if relevant)

Prevent the message "This email address is already subscribed." from appearing in the logs.

Manual testing scenarios (*)

1. Subscribe an email address that already exists.
2. You will see the error message (good), but it will also appear in the logs (unwanted)

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-engcom-team]

Hi @woutersamaey. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me 2.3-develop instance - deploy vanilla Magento instance

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[woutersamaey]

Fixed a typo, squashed commits and force pushed it.

[woutersamaey]

Added an extra space for codacy + squashed and force pushed it

[orlangur]

@woutersamaey looks good now 👍 You fixed "}else" before I finished a comment :)

[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-3565 has been created to process this Pull Request

[woutersamaey]

Hurray!

[woutersamaey]

Codacity does not like my else statement, but I don't really see a way around it. What's next @orlangur ?

[orlangur]

@woutersamaey TBH, this is pretty stupid rule and Codacy may be ignored in general.

[Dharmeshvaja91]

@woutersamaey i still able to reproduce the issue after apply your solution

[woutersamaey]

@Dharmeshvaja91 Okay, I saw you got a handle on this in #19404. Will leave it to you then.

[Dharmeshvaja91]

@woutersamaey Ok thank you, I will take care of it.