tests: remove unused os package import

os package is imported by every test script but only used by
a few, thus flake8 check reported errors.

tests/bench_msg_pingpong/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bench_mutex_pingpong/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bench_sched_nop/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bench_thread_flags_pingpong/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bench_thread_yield_pingpong/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bitarithm_timings/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/bloom_bytes/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/buttons/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/cb_mux/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/cb_mux_bench/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/cbor/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 ACCEPTED_ERROR = 20

tests/cpp11_condition_variable/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/cpp11_mutex/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/cpp11_thread/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/driver_ds1307/tests/01-run.py

@@ -6,7 +6,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/driver_grove_ledbar/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/driver_hd44780/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/driver_my9221/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/events/tests/01-run.py

@@ -7,7 +7,6 @@
 # General Public License v2.1. See the file LICENSE in the top level
 # directory for more details.
 
-import os
 import sys
 
 

tests/evtimer_msg/tests/01-run.py

@@ -7,7 +7,6 @@
 # directory for more details.
 
 from __future__ import print_function
-import os
 import sys
 
 ACCEPTED_ERROR = 20