Explanation: there are a few config-xy files in lib/idlelib that contain default configuration values. Custom values for a particular user, which override the defaults, are kept in a .idlerc directory placed in a users home directory (here C:/users/Tomk).  Config-main and config-keys are edited by Idle in response to entries in the preferences/options dialog. Any can be edited by hand.

Since Idle can work without these files, I consider it a bug that it quits when there is a bad one. Instead of raising an uncaught exception, it should display a warning message and continue*. It could also offer to delete or rename the file so the message does not reappear the next time Idle is started.

* (Note to myself) This could be done either by replacing the raise statement or by catching the exception further up the call chain, where other errors could be caught too, and all turned into warnings.

We are actively working on improving the error handling for config-keys, but I don't know if there is an issue for this particular error. So I am re-opening this issue until this problem is fixed or I know that this is a duplicate report. 

Thomas, thank you for the report, and in particular for the full traceback. when you reply by email, please delete the message you are responding to except possibly for a line or two that you need to quote. When viewed on the site, your response is placed just beneath the previous one, so bulk quoting is redundant.