Fix trivial PEP8 compliance errors

app/_logging.py

app/cli.py

app/commands/cmd_bot.py

app/commands/cmd_execute.py

app/commands/cmd_server.py

buildgrid/_exceptions.py

buildgrid/bot/bot.py

buildgrid/bot/bot_interface.py

buildgrid/bot/bot_session.py

buildgrid/server/action_cache.py

buildgrid/server/build_grid_server.py

buildgrid/server/cas/bytestream_service.py

buildgrid/server/cas/content_addressable_storage_service.py

buildgrid/server/cas/storage/disk.py

buildgrid/server/cas/storage/lru_memory_cache.py

buildgrid/server/cas/storage/s3.py

buildgrid/server/cas/storage/storage_abc.py

buildgrid/server/cas/storage/with_cache.py

buildgrid/server/execution/_exceptions.py

buildgrid/server/execution/action_cache_service.py