Exchange 2013 CU Installation: Setup can't continue with the upgrade because the mscorsvw (14664) has open files.
When installing an Exchange 2013 CU, the server was pending a reboot. After the reboot and rerunning:
Setup /m:upgrade /IAcceptExchangeServerLicenseTerms
I got the following error:
Setup can't continue with the upgrade because the mscorsvw (14664) has open files. Close the process, and then restart Setup. For more information, visit: http://technet.microsoft.com/library(EXCHG.150)/ms.exch.setupreadiness.ProcessNeedsToBeClosedOnUpgrade.aspx
The mscorsvw.exe is responsible for precompiling .NET assemblies. All I needed to do was wait for the process to complete, then all was well.