`xcode-select --install` failing
The other answer in the thread you linked is one of the possible solutions. It seems the installer will also display this message if your Command Line Tools are current and there are no updates available.
To check whether this is the case for you, check whether /usr/lib/tclConfig.sh exists on your system. Only the Command Line Tools contain this file on Mavericks, so if you have it, you also have the Command Line Tools installed.