Resolve "Fix error write (link to python3)"

Closes #43 (closed)

python/s2snow/utils.py

@@ -55,7 +55,8 @@ def call_subprocess(process_list):
         stderr=subprocess.PIPE)
     out, err = process.communicate()
     logging.info(out)
-    sys.stderr.write(err)
+    logging.error(err)
+    sys.stderr.write(str(err))
 
 def str_to_datetime(date_string, format="%Y%m%d"):
     """ Return the datetime corresponding to the input string