test harness: a few python3 fixes
test harness: a few python3 fixes

- Add decode() to output from subprocess so it's a string and not a byte-like
object (this causes exceptions when string methods are called on it from
tests)
- Flush stdout when printing test name so it shows up before test finshes
(otherwise it's blank during long tests)

[ci skip]

jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor