Content pack download gives odd messages

[benjaoming]

Summary

Downloading the Xhosa language pack rendered a message with a missing space, and then an "Update cancelled successfully" although it's unclear what that meant.. since I didn't request to cancel anything. Perhaps an already-running job was automatically cancelled, who knows.

Finally, after reloading the page, the content pack was installed, but there was no feedback.

This bug is mainly about the lack of feedback or otherwise unreliable feedback mechanism.

Branch or installer method

• Branch: 0.16.x

Traceback or relevant snippet from server.log

[INFO] [2016-08-01 12:44:07,753] django.request: HTTP Request /securesync/api/info - Response: 200
[INFO] [2016-08-01 12:48:56,034] django.request: HTTP Request /api/languagepacks/start - Response: 200
[INFO] [2016-08-01 12:48:56,148] kalite: Cancelling process retrievecontentpack
[INFO] [2016-08-01 12:48:57,297] kalite: Downloading content pack.
[INFO] [2016-08-01 12:48:57,423] kalite: Downloading content pack from http://pantry.learningequality.org/downloads/ka-lite/0.16/content/contentpacks/xh.zip
[INFO] [2016-08-01 12:48:57,451] django.request: HTTP Request /api/languagepacks/installed - Response: 200
[INFO] [2016-08-01 12:48:59,907] kalite: Moving content files to the right place.
[WARNING] [2016-08-01 12:49:00,628] kalite: No xh_icu.js file found in locale_path /home/pi/.kalite/locale
[WARNING] [2016-08-01 12:49:00,639] kalite: No xh_icu.js file found in locale_path /home/pi/.kalite/locale
[INFO] [2016-08-01 12:49:00,641] kalite: Writing i18nized js file to /home/pi/.kalite/content/locale/js/i18n/xh.js
[INFO] [2016-08-01 12:49:01,395] kalite: Looking for available content items.
[INFO] [2016-08-01 12:49:01,758] kalite: Annotating content for language: xh, channel: khan

This may take several minutes depending on system resources...
[INFO] [2016-08-01 12:49:05,080] kalite: Annotation complete for language: xh, channel: khan
[INFO] [2016-08-01 12:49:05,081] kalite: Finished processing content pack.
[INFO] [2016-08-01 12:52:03,675] django.request: HTTP Request /update/languages/ - Response: 200
[INFO] [2016-08-01 12:53:10,298] django.request: HTTP Request /update/languages/ - Response: 200
[INFO] [2016-08-01 12:53:11,510] django.request: HTTP Request /_generated/dynamic.css - Response: 200
[INFO] [2016-08-01 12:53:11,526] django.request: HTTP Request /_generated/dynamic.js - Response: 200
[INFO] [2016-08-01 12:53:12,272] django.request: HTTP Request /api/languagepacks/installed - Response: 200
[INFO] [2016-08-01 12:53:12,306] django.request: HTTP Request /securesync/api/user/status/ - Response: 200
[INFO] [2016-08-01 12:53:13,608] django.request: HTTP Request /securesync/api/info - Response: 200

How to reproduce

1. Start a content pack download job
2. Start another one

Screenshots

Real-life consequences (anything community should be aware, for instance how it affects your deployment)

In this case, the problem happened after upgrading KA Lite, whereby apparently an old job was stuck in the scheduler.

[benjaoming]

Not fixing this, should be part of the new scheduler #4892