Anomaly detection does not report errors

[palle-k]

Describe the bug
When running a task that completes with at least one error log output, the task is not marked as having any anomalies (as shown in the documentation) and an error_log_count of 0 is reported to web hooks.

The following messages have been logged:

Traceback (most recent call last):
ValueError: fake value error
2021-03-16 20:24:39 [root] ERROR this is some logged error message

The messages are highlighted in red and partially underlined in the task log shown on the Crawlab interface, indicating that they should have been detected as anomalies.

To Reproduce
Steps to reproduce the behavior:

1. Create a spider that produces some error log messages
2. Optional: Add a web hook to the spider
3. Run the spider

Expected behavior
The task should be reported as having produced an anomaly.

Notes

• The task was short running with a total run time of 2 seconds.
• Tried with latest master and 0.5.1 release

[tikazyq]

It could be short issue thing. You can try longer tasks, just in case.