strings.py: concat(): Perform substring operation on Unicode strings so that substring does not split Unicode characters. Still use to_raw_str() to calculate the str1 length because Unicode characters can be multi-byte, and length limits often apply to the byte length, not the character length.
strings.py: concat(): Perform substring operation on Unicode strings so that substring does not split Unicode characters. Still use to_raw_str() to calculate the str1 length because Unicode characters can be multi-byte, and length limits often apply to the byte length, not the character length.