Sentry: ignore logging known exceptions

By reading
https://docs.sentry.io/clients/python/integrations/#additional-settings it seems
that we should be able to ignore known exceptions to be sent to Sentry. Note
that we have this setting already defined at
https://github.com/readthedocs/readthedocs.org/blob/b5908b0fc65cb02fc840b23eeb4218b3115b6590/readthedocs/settings/base.py#L453

However, we need to add these known exceptions to
https://github.com/readthedocs/readthedocs.org/blob/b5908b0fc65cb02fc840b23eeb4218b3115b6590/readthedocs/projects/tasks/builds.py#L224-L229

This commit adds the known exceptions to be ignored by Celery and not sent to
Sentry either.

Author: humitos

readthedocs/projects/tasks/builds.py

@@ -220,12 +220,21 @@ class UpdateDocsTask(SyncRepositoryMixin, Task):
     max_retries = 5  # 5 per normal builds, 25 per concurrency limited
     default_retry_delay = 7 * 60
 
-    # Expected exceptions that will be logged as info only and not retried
+    # Expected exceptions that will be logged as info only and not retried.
+    # These exceptions are not sent to Sentry either because we are using
+    # ``SENTRY_CELERY_IGNORE_EXPECTED=True``.
+    #
+    # All exceptions generated by a user miss-configuration should be listed
+    # here. Actually, every subclass of ``BuildUserError``.
     throws = (
         DuplicatedBuildError,
         ProjectBuildsSkippedError,
         ConfigError,
         YAMLParseError,
+        BuildUserError,
+        RepositoryError,
+        MkDocsYAMLParseError,
+        ProjectConfigurationError,
     )
 
     acks_late = True