test_SendKeys: replace null-byte strings with "\x" representation, fix testANSIExtendedCharacters, fix Py3
test_SendKeys: replace null-byte strings with "\x" representation, fix testANSIExtendedCharacters, fix Py3

mindw/pywinauto,airelil/pywinauto,drinkertea/pywinauto,MagazinnikIvan/pywinauto,cetygamer/pywinauto,moden-py/pywinauto,pywinauto/pywinauto,moden-py/pywinauto,vasily-v-ryabov/pywinauto,mindw/pywinauto