Upgraded successfully from 16.04 to 18.04, then followed the tutorial for upgrade from 18.04 to 20.04. do-release-upgrade fails with “ERROR doUpdate() failed completely”. Lots of “ERROR IOError/SystemError”, but this one caught my eye:
ERROR IOError/SystemError in cache.update(): 'E:Failed to fetch https://repos.sonar.digitalocean.com/apt/dists/main/main/Contents-amd64.gz File has unexpected size (200 != 135). Mirror sync in progress? [IP: 188.8.131.52 443]
Where to start debugging this problem?
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