Fix bandit in python 3.8

[Stannislav]

Here are the changes:

Reformat code to make it pass under python3.8

Currently the # nosec directives don't work for multi-line strings in python3.8 (issue reported here PyCQA/bandit#658)

In order for it to work, the # nosec directive has to be placed on the first line of the expression, which is impossible for multi-line strings. Therefore the affected multi-line strings were converted to single-line strings.

Rename .bandit to .bandit.yml

The bandit configuration files seem to be a mess. According to the documentation on PyPI one can place a .bandit file into the working directory. In the example they provide it's an INI-style file. However bandit doesn't seem to read this file, contrary to what is written in the documentation.

Additionally, bandit has the -c command line option, that allows the specification of a configuration file. This is the way we configure bandit in our tox.ini. However, this file is a YAML-style config file, see here. Therefore I added the .yml extnesion to make this clear.

Pinned the bandit version in tox.ini

Seems like a good practise, just to avoid differences between run on different machines.

[EmilieDel]

LGTM! Thanks for doing this, Stan! 😄

[jankrepl]

Great! Thank you:)