What is this Xterm Error?

You've upgraded the OS and now you get this mysterious error

Failed to execute child process "xterm" (No such file or directory)

What does it mean?

Its a bug in the operating system installation package. Xterm is another terminal programme, but normally Raspian uses lxterminal which is more user-friendly.

What's the fix?

The quick fix is as follows. Open a terminal window and type

sudo ln -s /usr/bin/lxterminal /usr/bin/xterm

This creates a shortcut (soft-link in unix terms) to lxterminal.