Upgrading to 8.1 (from 5.7.5.12) yields this error.

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Declaration of BproModels\SourceConfig::Save() should be compatible with BproLibraries\Model::Save($generateCSS = true, $markAsUpdated = true)

The whole site is now down -

what to do?

 
rge replied on at Permalink Reply
The BproModel and BproLibraries namespace is not part of the Concrete core. So I assume you have installed a package.

I would advice to install the latest version of of the package and check if it is compatible with Concrete 8.