Error message improvement, not operator

Hi,

I recently got this error

`Syntax error: Error at line 27, position 71: Dangling expression after 'not'.`

which I found confusing because the word 'not' did appear only in a different line. It took me a while to realize that the ! operator was meant. Maybe change into 

`Syntax error: Error at line 27, position 71: Dangling expression after negation ('!').`

Best,
Sebastian