scripts: Add flake8 checker

Add code and style checker flake8.

Signed-off-by: Daniel Wagner <daniel.wagner@siemens.com>

scripts/checkcode.sh

@@ -5,6 +5,9 @@ ERROR=0
 echo "Checking with pycodestyle"
 pycodestyle --ignore=W503,W606 $1/*.py $1/*/*.py || ERROR=$(expr $ERROR + 1)
 
+echo "Checking with flake8"
+flake8 $1 || ERROR=$(expr $ERROR + 2)
+
 echo "Checking with doc8"
 doc8  $1/docs --ignore-path $1/docs/_build || ERROR=$(expr $ERROR + 4)