All: remove str import as it is not need

examples/mav2pcap.py

examples/mavtest.py

generator/mavgen_c.py

generator/mavgen_cs.py

generator/mavgen_java.py

generator/mavgen_javascript.py

generator/mavgen_python.py

generator/mavgen_wlua.py

generator/mavparse.py

generator/mavtemplate.py

mavparm.py

mavutil.py

quaternion.py

tools/magfit_rotation_gyro.py

tools/mavflightmodes.py

tools/mavkml.py

tools/mavlogdump.py

tools/mavparms.py

tools/mavplayback.py