Don't try to play with file.readline() - that seems to be working for
usual cases, but:

1. it does not work for cases when e.g. a dot is printed for every test
   run on the same line (e.g. neo/py tests, pytest, etc...)

2. in case when there is a lot of output available ready to be read it
   would be a waste of resources to read/flush it line by line.

-> use raw OS read with sane semantics.