qa: resolve failure in test 1720 relating to python binary I/O bufsize
qa: resolve failure in test 1720 relating to python binary I/O bufsize

Test tickled this https://bugs.python.org/issue32236 with python 3.8;
resolved by explicitly indicating we expect text output on the pipe,
not binary.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp