How to Fix iTunes Error -45076 macOS UpDate to High Sierra. iTunes can't open.

What is iTunes error -45076, and how might one fix the problem? I have already searched Apple and AskDifferent for the specific error code, but come up empty handed.


macOS High Sierra was install on Sept 26, 2017.
iTunes 12.6.2


iTunes starts, displays the error, as shown below, and leaves no option but to quit. It tried before and after the High Sierra update: iTunes was working before the High Sierra update today.



Starting iTunes from a terminal (/Applications/iTunes.app/Contents/MacOS/iTunes) 
yields the following output: 2017-09-26 22:09:09.802 iTunes[930:14353] .sdef warning for attribute 'rawData' of class 'artwork' in suite 'iTunes Suite': 'raw data' is not a valid type name.
Here's how to fix error -45076 if you have downgraded iTunes 12.7 to 12.6.2 still under Sierra and have then upgraded your OS to High Sierra: 


Re-download the iTunes 12.6.2-DMG directly from the Apple Servers.
Make a backup of ~/Music/iTunes/iTunes Library.itl (just in case).
Delete iTunes 12.6.2 from your High Sierra Mac, this time entirely (list of ingredients courtesy of macrumours.com member driveparty):sudo rm -rf
/Library/Documentation/Applications/iTunes/Acknowledgements.rtf
/Library/Documentation/iPod/Acknowledgements.rtf
/Library/Frameworks/iTunesLibrary.framework/
/Applications/iTunes.app/
/System/Library/PrivateFrameworks/iTunesAccess.framework/
/System/Library/LaunchDaemons/com.apple.fpsd.plist
/System/Library/PrivateFrameworks/CoreFP.framework/
/System/Library/PrivateFrameworks/CoreADI.framework/
/System/Library/LaunchDaemons/com.apple.adid.plist
/System/Library/CoreServices/UAUPlugins/ADIUserAccountUpdater.bundle/
/System/Library/CoreServices/CoreTypes.bundle/Contents/Library/MobileDevices.bundle/
/System/Library/LaunchDaemons/com.apple.usbmuxd.plist
/System/Library/PrivateFrameworks/AirTrafficHost.framework/
/System/Library/PrivateFrameworks/DeviceLink.framework/
/System/Library/PrivateFrameworks/MobileDevice.framework/
/System/Library/Extensions/AppleMobileDevice.kext/
/System/Library/Extensions/AppleUsbEthernetHost
Install iTunes 12.6.2 again from the DMG downloaded above.