We're Hiring!

Mattermost, Inc.

No attachments in mattermost after import of Slack Advanced Exporter file via CLI or mmetl

Summary
All post attachments (images/pdfs/mp4) are missing after import to mattermost

Steps to reproduce
https://docs.mattermost.com/administration/migrating.html#migrating-from-slack-using-the-mattermost-cli
Download Slack export from Slack.
Download attachments via Slack Advanced Exporter. The export-with-attachments.zip has all the files in the __uploads folder.

sudo ./slack-advanced-exporter-linux-amd64 --input-archive slack.zip --output-archive export-with-attachments.zip fetch-attachments

Import resulting archive to Mattermost 5.24.2 using CLI tool

/opt/mattermost/bin/mattermost import slack testteam /root/export-with-attachments.zip

After performing the above steps I verified the newly imported team. All the messages are in place, except for attachments. Those were completely missing.

Debian 10
Mattermost 5.24.2

Expected behavior
The mattermost channel has all the attachments like the slack channel.

Mattermost Slack Import Log
#######
{"level":"info","ts":1597277647.6629498,"caller":"utils/i18n.go:83","msg":"Loaded system translations","for locale":"en","from locale":"/opt/mattermost/i18n/en.json"}
{"level":"info","ts":1597277647.6632302,"caller":"app/server_app_adapters.go:58","msg":"Server is initializing..."}
{"level":"info","ts":1597277647.6673126,"caller":"sqlstore/supplier.go:227","msg":"Pinging SQL","database":"master"}
{"level":"error","ts":1597277647.7305863,"caller":"app/server_app_adapters.go:152","msg":"Mail server connection test is failed: SendEmailNotifications is not true"}
{"level":"info","ts":1597277647.7317753,"caller":"app/license.go:37","msg":"License key from https://mattermost.com required to unlock enterprise features."}
{"level":"info","ts":1597277647.7370763,"caller":"mlog/log.go:167","msg":"Starting up plugins"}
{"level":"error","ts":1597277647.737134,"caller":"app/plugin.go:161","msg":"Failed to start up plugins","error":"mkdir ./client/plugins: no such file or directory"}
{"level":"info","ts":1597277647.7371817,"caller":"app/server.go:273","msg":"Current version is 5.24.0 (5.24.2/Fri Jun 26 19:10:02 UTC 2020/2c394d78ca036a439aa06fedd6ad187da535d5fc/8239891909042ef8e47e2b81b5d515ec65d8938c)","current_version":"5.24.0","build_number":"5.24.2","build_date":"Fri Jun 26 19:10:02 UTC 2020","build_hash":"2c394d78ca036a439aa06fedd6ad187da535d5fc","build_hash_enterprise":"8239891909042ef8e47e2b81b5d515ec65d8938c"}
{"level":"info","ts":1597277647.7372105,"caller":"app/server.go:282","msg":"Enterprise Build","enterprise_build":true}
{"level":"info","ts":1597277647.7372365,"caller":"app/server.go:288","msg":"Printing current working","directory":"/root"}
{"level":"info","ts":1597277647.7372603,"caller":"app/server.go:289","msg":"Loaded config","source":"file:///opt/mattermost/config/config.json"}
{"level":"info","ts":1597277647.7566736,"caller":"sqlstore/post_store.go:1571","msg":"Post.Message has size restrictions","max_characters":16383,"max_bytes":65535}
{"level":"info","ts":1597277647.7570834,"caller":"mlog/log.go:167","msg":"Starting up plugins"}
{"level":"error","ts":1597277647.7571416,"caller":"app/plugin.go:161","msg":"Failed to start up plugins","error":"mkdir ./client/plugins: no such file or directory"}
{"level":"info","ts":1597277647.7919083,"caller":"mlog/log.go:167","msg":"Starting up plugins"}
{"level":"error","ts":1597277647.791985,"caller":"app/plugin.go:161","msg":"Failed to start up plugins","error":"mkdir ./client/plugins: no such file or directory"}
{"level":"info","ts":1597277647.7944965,"caller":"bleveengine/bleve.go:267","msg":"UpdateConf Bleve"}
{"level":"info","ts":1597277647.795125,"caller":"app/license.go:37","msg":"License key from https://mattermost.com required to unlock enterprise features."}
{"level":"info","ts":1597277647.7955935,"caller":"mlog/log.go:167","msg":"Starting up plugins"}
{"level":"error","ts":1597277647.7956364,"caller":"app/plugin.go:161","msg":"Failed to start up plugins","error":"mkdir ./client/plugins: no such file or directory"}
Running Slack Import. This may take a long time for large teams or teams with many messages.
{"level":"info","ts":1597277648.0550404,"caller":"app/admin.go:151","msg":"Purging all caches"}
{"level":"info","ts":1597277648.05632,"caller":"app/license.go:37","msg":"License key from https://mattermost.com required to unlock enterprise features."}

Mattermost Slack Import Log

Users created:
===============

Slack user merged with an existing Mattermost user with matching email *** and username ***.
The Integration/Slack Bot user with email slackimportuser_xdbe9txcrbr3bk58og196ze4te@localhost and password *** has been imported.

Channels added:
=================

zufällig
slackexport
testbilder2
allgemein

Notes:
=======

- Some messages may not have been imported because they were not supported by this importer.
- Slack bot messages are currently not supported.
- Additional errors may be found in the server logs.


Finished Slack Import.

{"level":"info","ts":1597277648.0575478,"caller":"app/server.go:416","msg":"Stopping Server..."}
{"level":"info","ts":1597277648.05758,"caller":"app/web_hub.go:130","msg":"stopping websocket hub connections"}
{"level":"info","ts":1597277648.0584583,"caller":"app/server.go:469","msg":"Server stopped"}