Ensure SNS message sent if email sent for prod

[hwine]

Received an email for an S3 failure in prod, but no page occurred. (Message details in #61.)

Possible causes:

• ~SNS went to wrong pager number (Hal's old phone)~ confirmed good numbers in system
• SNS not requested by code path

[hwine]

email text:

From: FxSigAlert <no-reply@sns.amazonaws.com>
Date: Mon, Sep 9, 2019 at 6:50 AM
Subject: fail for s3: ... firefox-71.0a1.son.win32.installer.exe
To: 

fail for s3://net-mozaws-prod-delivery-firefox/pub/firefox/nightly/latest-mozilla-central-l10n/firefox-71.0a1.son.win32.installer.exe
errors:
    failed to process s3 object net-mozaws-prod-delivery-firefox/pub/firefox/nightly/latest-mozilla-central-l10n/firefox-71.0a1.son.win32.installer.exe 'ProtocolError("Connection broken: error(104, 'Connection reset by peer')", error(104, 'Connection reset by peer'))'
firefox-71.0a1.son.win32.installer.exe
key=pub/firefox/nightly/latest-mozilla-central-l10n/firefox-71.0a1.son.win32.installer.exe
bucket=net-mozaws-prod-delivery-firefox