calibre-debug print fails

[qqqqqqqqq9]

In calibre 3.31

I get this:

$ /usr/bin/calibre-debug -c"print 'ffff'"

ffff

In calibre 3.34, it fails:

$ /usr/bin/calibre-debug -c"print 'ffff'"
Traceback (most recent call last):
  File "/usr/bin/calibre-debug", line 20, in <module>
    sys.exit(main())
  File "/usr/lib/calibre/calibre/debug.py", line 276, in main
    exec(opts.command)
  File "<string>", line 1
    print 'ffff'
               ^
SyntaxError: invalid syntax

System: Ubuntu Disco