init: use the Python 3 compatible string type

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@71393 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/init/grass.py

@@ -1373,10 +1373,10 @@ def run_batch_job(batch_job):
     :param batch_job: executable and parameters in a list or a string
     """
     batch_job_string = batch_job
-    if not isinstance(batch_job, basestring):
+    if not isinstance(batch_job, string_types):
         batch_job_string = ' '.join(batch_job)
     message(_("Executing <%s> ...") % batch_job_string)
-    if isinstance(batch_job, basestring):
+    if isinstance(batch_job, string_types):
         proc = Popen(batch_job, shell=True)
     else:
         try: