In order to workaround T121490 I have symlinked "vector" in the "skins" directory to "Vector".
The CLI installer went fine, but running `update.php` fails with
`Exception encountered, of type "InvalidArgumentException"`
The stacktrace:
````
[5323b2ec] [no req] InvalidArgumentException from line 88 of /usr/home/saper/public_html/collaps/includes/config/ConfigFactory.php: Invalid callback provided
Backtrace:
#0 /usr/home/saper/public_html/collaps/includes/config/ConfigFactory.php(59): ConfigFactory->register(string, array)
#1 /usr/home/saper/public_html/collaps/maintenance/doMaintenance.php(100): ConfigFactory::getDefaultInstance()
#2 /usr/home/saper/public_html/collaps/maintenance/update.php(214): require_once(string)
#3 {main}
````
What happens is that vector is added twice to `$wgConfigRegistry`:
````
array(2) {
["vector"]=>
array(2) {
[0]=>
string(28) "GlobalVarConfig::newInstance"
[1]=>
string(28) "GlobalVarConfig::newInstance"
}
["main"]=>
string(28) "GlobalVarConfig::newInstance"
}
````
MediaWiki core: 5b0ebd7f3a6e1c215a6af56d966ee14047a9b44f