tests: change blackbox test to work cross platform
While it is not easy to make a file 000 on Windows, you can
emulate most of the behaviors by replacing the file with a directory.
Also corrects test description to properly indicate that failing to
read from the log is fatal.
FROM debian:jessie
RUN apt-get update && apt-get install -y \
build-essential \
debhelper \
dh-python \
devscripts \
python \
python-all-dev \
python-docutils \
zip \
unzip