base_hooks_service.rb

When a pipeline fails to create in `PostReceive`, the error is silently
discarded, making it difficult to understand why a pipeline was not
created. We now add a Sidekiq warning message for this. Adding a Sentry
exception when this happens would generate a lot of noise for invalid CI
files.

Relates to https://gitlab.com/gitlab-org/gitlab-ee/issues/14720