Proofread Page is now able to create automatically Page and Index namepaces with internationalized names taken in its i18n file using numbers set in $wgProofreadPageNamespaceIds .
So, we can now remove creation of Page and Index namespaces in $wgExtraNamespaces and setup of English aliases in $wgNamespaceAliases in order to let the extension create these two namespaces.
The wikis affected is all Wikisources that doesn't use the default Proofread Page namespaces (Wikisources created since Novemeber 2012), test2 and frr Wikipedia.
Note: test2 doesn't use currently $wgProofreadPageNamespaceIds but the auto-detection of the namespace system. It may be a good idea to move it to the new system before the other wikis in order to test if the code that create namespaces works well.