add possibility to specify subprocess stdout encoding

fix deadlock if method kill() is called after process is already finished

fix pylint py3k conversion warning: "(no-absolute-import) import missing `from __future__ import absolute_import`"

make CanFestival to be at the expected place in bitbucket pipelines container

fix pylint error '(unsubscriptable-object) Value 'X' is unsubscriptable'

fix pylint warning '(bad-continuation) Wrong hanging indentation before block'

force all python source code to have LF line ending

fix pylint warning '(expression-not-assigned) Expression "X" is assigned to nothing'

fix pylint warning '(redefine-in-handler) Redefining name 'X' from outer scope (line Y) in exception handler'

fix displaying result of update check during Beremiz startup

fix pylint warning '(no-init) Class has no __init__ method'

fix pylint error "(undefined-variable) Undefined variable 'X'"