Would it not be nice to see the offending string

What do you mean by "the offending string"? Do you mean the line of code? Because that error message says there's a problem with the code, not with whatever string (data) was being operated upon by the regex.

in an error code

What do you mean by "an error code"? Do you mean "the error message"? i.e. the line which is printed by the interpreter.