Fix pylint warnings in art_apex_test

* Don't shadow global variables
* Remove unnecessary semicolons
* Do not use `len()` to determine if a sequence is empty
* Replace some if statements with test
* Remove unused variables
* Remove useless super methods
* Switch to enumerate where possible
* Make some class members public
* Restrict exceptions coming from zip
* Remove not checked boolean function returns

* Long lines were untouched

Test: art/build/apex/runtests.sh
Change-Id: I247ee2ba5903ae69f478dbfc5517a39c3f5e9e0e