pep8 fixes for kivy/uix/button.py
pep8 fixes for kivy/uix/camera.py
pep8 fixes for kivy/uix/carousel.py
pep8 fix for kivy/uix/checkbox.py
pep8/grammar fixes in kivy/uix/codeinput.py
pep8 fixes for kivy/uix/colorpicker.py
pep8 fixes in kivy/uix/dropdown.py