This is copied from the talk page:
The hitcounter table has been removed completely between 1.25.3 and 1.26.0 of MediaWiki and so the statement in rename_table.sql fails and the HCUpdater.php script gives up.
Not a problem if you've already installed the HitCounters extension before upgrading to 1.26.0. We didn't though so now we can't install it. I'd suggest some error checking in HCUpdater.php and if the hitcounter table doesn't exist, create the hit_counter table from scratch. Otherwise as more users upgrade to the latest version of MW, fewer people will be able to install this extension. That's possibly the intention given the dubious utility of these counts but in that case, it's probably best to put a note in the installation intructions.