Location of an Error Message

[stehlampen at arcor.de]

Where are the error messages stored? E. g., in which (source code) file is the message "NameError: name 'sdfe' is not defined" stored (except for variable arguments like "sdfe")? I do know that I can throw exceptions for myself, but this question came to my mind in thinking about translating the error messages to improve Python's learning curve for newbies.
Additionally, I would be grateful if you would give to me the file name (e. g. in hg.python.org) which is the Interpreter's first piece of source code which deals with the error strings.

Many thanks in advance!