/usr/sbin/sendmail: not found in sidekiq

Summary

Enabling SMTP support for outbound notifications on CNG based sidekiq image causes outbound failures as sendmail isn't install and seems to be required.

Steps to reproduce

Enabled SMTP email delivery using latest CNG chart.

Configuration used

I tend to use --set versus modifying the values.yaml files directly.

	helm upgrade --install gitlab gitlab --recreate-pods \
        --timeout 600 \
        --set global.hosts.domain=xxxxxx \
        --set global.hosts.gitlab.name=git.xxxxxx \
        --set global.hosts.registry.name=hub.xxxxxx \
        --set global.email.from=git@xxxxxx \
        --set global.smtp.enabled=false \
        --set global.smtp.port=587 \
        --set global.smtp.authentication=login \
        --set global.smtp.domain=xxxxxx \
        --set global.smtp.starttls_auto=true \
        --set global.smtp.address=email-smtp.us-west-2.amazonaws.com \
        --set global.smtp.user_name=xxxxxx \
        --set global.smtp.password.secret=xxxxxx \
        --set certmanager-issuer.email=xxxxxx@xxxxxx

Current behavior

After enabling SMTP via AWS's SES service a simple test of doing a "forgot my password" reset, which then seems successful to the user, yet no email is delivered.

Expected behavior

Successful email to be sent via SMTP.

.## Versions

• Chart: 1.3.3
• Platform:
  • Cloud: AWS
  • Self-hosted: KOPS
• Kubernetes:
  • Client:1.12.3
  • Server:1.12.3
• Helm:
  • Client: 2.11.0
  • Server: 2.11.0

Relevant logs

2018-12-14T04:30:18.428Z 9 TID-gtn5hkfkt ActionMailer::DeliveryJob JID-8d348a44d1ff6f1aa0c64fa9 INFO: start
[ActiveJob] [ActionMailer::DeliveryJob] [815e2cef-5470-4ed7-ba81-69e488cdccf3] Performing ActionMailer::DeliveryJob from Sidekiq(mailers) with arguments: "DeviseMailer", "reset_password_instructions", "deliver_now", gid://gitlab/User/2, "xxxxxxx", {}
sh: 1: /usr/sbin/sendmail: not found
[ActiveJob] [ActionMailer::DeliveryJob] [815e2cef-5470-4ed7-ba81-69e488cdccf3]
Sent mail to xxxx@xxxxx.com (4.4ms)
[ActiveJob] [ActionMailer::DeliveryJob] [815e2cef-5470-4ed7-ba81-69e488cdccf3] Performed ActionMailer::DeliveryJob from Sidekiq(mailers) in 443.03ms
2018-12-14T04:30:18.919Z 9 TID-gtn5hkfkt ActionMailer::DeliveryJob JID-8d348a44d1ff6f1aa0c64fa9 INFO: done: 0.49 sec