fix: linter errors for bench/

Author: M0r13n

.flake8

@@ -4,4 +4,4 @@ ignore = E501
 show_source = True
 statistics = True
 count = True
-exclude = .direnv,.git,__pycache__,venv,.eggs,.venv
+exclude = .direnv,.git,__pycache__,venv,.eggs,.venv,bench/build

bench/bench_libais.py

@@ -1,10 +1,7 @@
-from pyais.exceptions import UnknownMessageException
-from pyais import FileReaderStream
 from collections import defaultdict
 import time
 import pathlib
 import ais.stream
-import json
 import ais.compatibility.gpsd
 
 file = pathlib.Path(__file__).parent.joinpath('../tests/nmea-sample')