tools/power/x86/intel_pstate_tracer: python minimum version

Change the minimum python version from 2.7 to 3.6.
Remove a 2.X backwards compatibility line.

Signed-off-by: Doug Smythies <[e-mail]>
Acked-by: Srinivas Pandruvada <[e-mail]>
Reviewed-by: Mario Limonciello <[e-mail]>
Tested-by: Swapnil Sapkal <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

tools/power/x86/intel_pstate_tracer/intel_pstate_tracer.py

···
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0-only
 # -*- coding: utf-8 -*-
 #
···
 and generates performance plots.
 
 Prerequisites:
-    Python version 2.7.x or higher
+    Python version 3.6.x or higher
     gnuplot 5.0 or higher
-    gnuplot-py 1.8 or higher
+    python3-gnuplot 1.8 or higher
     (Most of the distributions have these required packages. They may be called
-     gnuplot-py, phython-gnuplot or phython3-gnuplot, gnuplot-nox, ... )
+     gnuplot-py, python-gnuplot or python3-gnuplot, gnuplot-nox, ... )
 
     HWP (Hardware P-States are disabled)
     Kernel config for Linux trace is enabled
···
     see print_help(): for Usage and Output details
 
 """
-from __future__ import print_function
+
 from datetime import datetime
 import subprocess
 import os
···
 
     # Temporary (or perhaps not)
     cur_version = sys.version_info
-    print('python version (should be >= 2.7):')
+    print('python version (should be >= 3.6):')
     print(cur_version)
 
     # Left as "cleanup" for potential future re-run ability.