Unable to start Plesk migration: urlopen error [Errno 99] Cannot assign requested address

Symptoms

Unable to start Plesk migration due to the following error:

urlopen error [Errno 99] Cannot assign requested address

Cause

Misconfigured IP address on the target server.

Plesk Migrator tries to check connection to the target host by taking the first IP from
IP_Addresses
table and trying to establish connection. If the first IP is misconfigured or does not exist on the target server, an error is returned.

Resolution

1. Log in to target Plesk server

2. Go to Tools & Settings > IP addresses and click Reread. Repair link should appear next to the problematic IP address. Click Repair or remove the address from Plesk.

3. Finish current migration with Tools & Settings >  Migration & Transfer Manager > Finish Migration, then start a new session.