symbolize.py: Python < 3.7 compatibility

The documentation for the Python 3 subprocess module [1] has the
following note related to the Popen() constructor:

 Changed in version 3.7: Added the text parameter, as a more
 understandable alias of universal_newlines.

In order to avoid a runtime error with versions of Python prior to 3.7,
replace the 'text' parameter with 'universal_newlines'.

Link: [1] https://docs.python.org/3/library/subprocess.html
Signed-off-by: Jerome Forissier <jerome@forissier.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
diff --git a/scripts/symbolize.py b/scripts/symbolize.py
index 206e820..4f5e226 100755
--- a/scripts/symbolize.py
+++ b/scripts/symbolize.py
@@ -106,7 +106,8 @@
     def my_Popen(self, cmd):
         try:
             return subprocess.Popen(cmd, stdin=subprocess.PIPE,
-                                    stdout=subprocess.PIPE, text=True,
+                                    stdout=subprocess.PIPE,
+                                    universal_newlines=True,
                                     bufsize=1)
         except OSError as e:
             if e.errno == errno.ENOENT: