Forum upgrading to 4.2 alpha 1 error

[محروم.كوم]

Upgrade was aborted!

Unexpected Text:

Fatal error: Call to undefined function build_activitystream_datastore() in /home/foreclos/public_html/install/includes/class_upgrade_420a1.php on line 599

• Upgrading to 4.2.0 Alpha 1
• Step 1 - Creating navigation table
• Step 2 - Altering cron Table (1 of 1)
• Step 3 - Altering user Table (1 of 1)
• Step 4 - Creating index lastactivity on user
• Step 5 - Creating contentread table
• Step 6 - Creating ipdata table
• Step 7 - Disable or Remove Old Products
• Step 8 - Altering block Table (1 of 1)
• Step 9 - Updating Usergroup Permissions
• Updating Usergroup Permissions
• Updating Usergroup Permissions
• Updating Usergroup Permissions
• Step 10 - Updating forum table
• Updating forum table
• Step 11 - Creating index script on upgradelog
• Step 12 - Creating activitystream table
• Step 13 - Creating activitystreamtype table
• Step 14 - Updating activitystreamtype table
• Step 15 - Altering language Table (1 of 1)
• Step 16 - Updating phrasetype table
• Step 17 - Altering picturecomment Table (1 of 3)
• Step 18 - Altering picturecomment Table (2 of 3)
• Step 19 - Altering picturecomment Table (3 of 3)
• Step 20 - Altering thread Table (1 of 1)

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