fix broken sys.stdout.write on modern python

[svmhdvn]

• Use sys.stdout.buffer.write as recommended by https://docs.python.org/3/library/sys.html to fix a bad write of an extra bad byte in hello42.tbf1 output.
• Use recommended with open(...) idiom to read file (also fixes a nonexistent file(...) call on modern python)
• Remove cgitb as it's deprecated and gone