TextEditor "evaluate" has bare except

See https://github.com/enthought/traitsui/blob/bcc1f99e8367905bcdc1b96da461dc4c0be559e6/traitsui/qt4/text_editor.py#L148-L151

This means user errors in custom evaluate functions are silently swallowed. This should at least log any errors, particularly if they aren't ValueErrors (maybe log value errors at debug, and other errors at info or error; some thought needed).

More generally we should audit for situations where we have user-supplied callbacks and we are not informing the user of errors when they run.