test/thread_basic: fix pep8 in testrunner script

tests/thread_basic/tests/01-run.py

@@ -12,6 +12,7 @@ import sys
 sys.path.append(os.path.join(os.environ['RIOTBASE'], 'dist/tools/testrunner'))
 import testrunner
 
+
 def testfunc(child):
     child.expect('first thread\r\n')
     child.expect('second thread\r\n')